<PAGE>

                                                                     Exhibit 4.7

THIS COMMON STOCK PURCHASE WARRANT AND THE SECURITIES REPRESENTED HEREBY HAVE
NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE
TRANSFERRED IN VIOLATION OF SUCH ACT, THE RULES AND REGULATIONS THEREUNDER OR
THE PROVISIONS OF THIS COMMON STOCK PURCHASE WARRANT.

                   Number of Shares of Common Stock: 150,000
                                 Warrant No. 1

                         COMMON STOCK PURCHASE WARRANT

                          To Purchase Common Stock of

                    American TeleSource International, Inc.

          This Is To Certify That The Shaar Fund Ltd., or registered assigns, is
entitled, at any time from the Closing Date (as hereinafter defined) to the
Expiration Date (as hereinafter defined), to purchase from American TeleSource
International, Inc., a Delaware corporation (the "Company"), 150,000 shares of
Common Stock (as hereinafter defined and subject to adjustment as provided
herein), in whole or in part, including fractional parts, at a purchase price
set forth herein, all on the terms and conditions and pursuant to the provisions
hereinafter set forth.

                                  Definitions
                                  -----------

          As used in this Common Stock Purchase Warrant (this "Warrant"), the
following terms have the respective meanings set forth below:

          "Additional Shares of Common Stock" shall mean all shares of Common
Stock issued by the Company after the Closing Date, other than Warrant Stock.

          "Amex" shall mean The American Stock Exchange.

          "Book Value" shall mean, in respect of any share of Common Stock on
any date herein specified, the consolidated book value of the Company as of the
last day of any month immediately preceding such date, divided by the number of
Fully Diluted Outstanding shares of Common Stock as determined in accordance
with GAAP (assuming the payment of the exercise prices for such shares) by
Arthur Andersen LLP or any other firm of independent certified public
accountants of recognized national standing selected by the Company and
reasonably acceptable to the Holder.

          "Business Day" shall mean any day that is not a Saturday or Sunday or
a day on which banks are required or permitted to be closed in the State of New
York.

          "Closing Date" shall have the meaning set forth in the Securities
Purchase Agreement.

          "Commission" shall mean the Securities and Exchange Commission or any
other federal agency then administering the Securities Act and other federal
securities laws.

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          "Common Stock" shall mean (except where the context otherwise
indicates) the Common Stock, par value $0.001 per share, of the Company as
constituted on the Closing Date, and any capital stock into which such Common
Stock may thereafter be changed, and shall also include (i) capital stock of the
Company of any other class (regardless of how denominated) issued to the holders
of shares of Common Stock upon any reclassification thereof which is also not
preferred as to dividends or assets over any other class of stock of the Company
and which is not subject to redemption and (ii) shares of common stock of any
successor or acquiring corporation received by or distributed to the holders of
Common Stock of the Company in the circumstances contemplated by Section 4.4.

          "Convertible Securities" shall mean evidences of indebtedness, shares
of stock or other securities which are convertible into or exchangeable, with or
without payment of additional consideration in cash or property, for shares of
Common Stock, either immediately or upon the occurrence of a specified date or a
specified event.

          "Current Market Price" shall mean, as of any date of determination,
the average of the closing prices of the Common Shares as reported on the Amex
for the five Trading Days immediately preceding such date of determination;
provided that, if such security is not listed on the Amex, the closing prices as
reported on the principal national security exchange or quotation system on
which such security is quoted or listed or admitted to trading (closing bid
prices in the case of a quotation system), or if not quoted or listed or
admitted to trading on any national securities exchange or quotation system, the
closing bid prices of such security on the over-the-counter market as reported
by Bloomberg LP, or a similar generally accepted reporting service, as the case
may be, for the five Trading Days immediately preceding such date of
determination.

          "Current Warrant Price" shall mean, in respect of a share of Common
Stock at any date herein specified, one hundred and fifteen percent (115%) of
the arithmetic mean of the lowest closing prices of a share of Common Stock as
reported on the Amex on five (5) Trading Days during the period of ten (10)
Trading Days immediately preceding February 17, 2000, it being understood that
such five (5) Trading Days need not be consecutive.

          "Exchange Act" shall mean the Securities Exchange Act of 1934, as
amended, or any successor federal statute, and the rules and regulations of the
Commission thereunder, all as the same shall be in effect from time to time.

          "Exercise Period" shall mean the period during which this Warrant is
exercisable pursuant to Section 2.1.

          "Expiration Date" shall mean February 22, 2005.

          "Fully Diluted Outstanding" shall mean, when used with reference to
Common Stock, at any date as of which the number of shares thereof is to be
determined, all shares of Common Stock Outstanding at such date and all shares
of Common Stock issuable in respect of this Warrant, outstanding on such date,
and other options or warrants to purchase, or securities convertible into,
shares of Common Stock outstanding on such date which would be deemed
outstanding in accordance with GAAP for purposes of determining Book Value or
net income per share.

          "GAAP" shall mean generally accepted accounting principles in the
United States of America as from time to time in effect.

          "Holder" shall mean the Person in whose name the Warrant or Warrant
Stock set forth herein is registered on the books of the Company maintained for
such purpose.

          "Market Price" per Common Share means the average of the closing
prices of the Common Shares as reported on the Amex for the five trading days
immediately preceding February 17, 2000.

          "Other Property" shall have the meaning set forth in Section 4.4.

                                      69
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          "Outstanding" shall mean, when used with reference to Common Stock, at
any date as of which the number of shares thereof is to be determined, all
issued shares of Common Stock, except shares then owned or held by or for the
account of the Company or any subsidiary thereof, and shall include all shares
issuable in respect of outstanding scrip or any certificates representing
fractional interests in shares of Common Stock.

          "Person" shall mean any individual, sole proprietorship, partnership,
joint venture, trust, incorporated organization, association, corporation,
institution, public benefit corporation, entity or government (whether federal,
state, county, city, municipal or otherwise, including, without limitation, any
instrumentality, division, agency, body or department thereof).

          "Registration Rights Agreement" shall mean the Registration Rights
Agreement dated a date even herewith between the Company and The Shaar Fund
Ltd., as it may be amended from time to time.

          "Restricted Common Stock" shall mean shares of Common Stock which are,
or which upon their issuance on their exercise of this Warrant would be,
evidenced by a certificate bearing the restrictive legend set forth in Section
9.1(a).

          "Securities Act" shall mean the Securities Act of 1933, as amended, or
any successor federal statute, and the rules and regulations of the Commission
thereunder, all as the same shall be in effect at the time.

          "Securities Purchase Agreement" shall mean the Securities Purchase
Agreement dated as of a date even herewith between the Company and The Shaar
Fund Ltd., as it may be amended from time to time.

          "Transfer" shall mean any disposition of any Warrant or Warrant Stock
or of any interest in either thereof, which would constitute a sale thereof
within the meaning of the Securities Act.

          "Transfer Notice" shall have the meaning set forth in Section 9.2.

          "Warrant Price" shall mean an amount equal to (i) the number of shares
of Common Stock being purchased upon exercise of this Warrant pursuant to
Section 2.1, multiplied by (ii) the Current Warrant Price as of the date of such
exercise.

          "Warrant Stock" shall mean the shares of Common Stock purchased by the
holders of the Warrants upon the exercise thereof.

          "Warrants" shall mean this Warrant and all warrants issued upon
transfer, division or combination of, or in substitution for, any thereof.  All
Warrants shall at all times be identical as to terms and conditions and date,
except as to the number of shares of Common Stock for which they may be
exercised.

                              Exercise of Warrant
                              -------------------
Manner of Exercise
------------------

          From and after the Closing Date and until 5:00 p.m., New York time, on
the Expiration Date, Holder may exercise this Warrant, on any Business Day, for
all or any part of the number of shares of Common Stock purchasable hereunder.

          In order to exercise this Warrant, in whole or in part, Holder shall
deliver to the Company at its principal office at 12500 Network Boulevard, Suite
407, San Antonio, Texas 78249, or at the office or agency designated by the
Company pursuant to Section 12, (i) a written notice of Holder's election to
exercise this Warrant, which notice shall specify the number of shares of Common
Stock to be purchased, (ii) to the extent such exercise is not being effected
through a Cashless Exercise, payment of the Warrant Price in cash or wire
transfer or cashier's check drawn on a United States bank and (iii) this
Warrant.  Such notice shall be substantially in the form of the subscription
form appearing at the end of this Warrant as Exhibit A, duly executed by Holder
or its agent or attorney.  Upon receipt of the items referred to in clauses (i),
(ii) and (iii) above, the Company shall, as promptly as practicable, and in any
event within five Business Days thereafter, execute or cause to be executed and
deliver or cause to be delivered to Holder a certificate or certificates
representing the aggregate number of full shares of

                                      70
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Common Stock issuable upon such exercise, together with cash in lieu of any
fraction of a share, as hereinafter provided. The stock certificate or
certificates so delivered shall be, to the extent possible, in such denomination
or denominations as Holder shall request in the notice and shall be registered
in the name of Holder or, subject to Section 9, such other name as shall be
designated in the notice. This Warrant shall be deemed to have been exercised
and such certificate or certificates shall be deemed to have been issued, and
Holder or any other Person so designated to be named therein shall be deemed to
have become a holder of record of such shares for all purposes, as of the date
the notice, provided that the cash or check or checks and this Warrant are
received by the Company as described above and all taxes required to be paid by
Holder, if any, pursuant to Section 2.2 prior to the issuance of such shares
have been paid. If this Warrant shall have been exercised in part, the Company
shall, at the time of delivery of the certificate or certificates representing
Warrant Stock, deliver to Holder a new Warrant evidencing the rights of Holder
to purchase the unpurchased shares of Common Stock called for by this Warrant,
which new Warrant shall in all other respects be identical with this Warrant,
or, at the request of Holder, appropriate notation may be made on this Warrant
and the same returned to Holder. Notwithstanding any provision herein to the
contrary, the Company shall not be required to register shares in the name of
any Person who acquired this Warrant (or part hereof) or any Warrant Stock
otherwise than in accordance with this Warrant.

          Simultaneously with the exercise of this Warrant, payment in full of
the Warrant Price may be made, at the option of the Holder, (i) by payment of
the Warrant Price in cash by wire transfer or cashier's check drawn on a United
States bank, (ii) by the surrender (which surrender shall be evidenced by
cancellation of the number of Warrants represented by any certificate(s)
evidencing the Warrants (the "Warrant Certificate") presented in connection with
a Cashless Exercise) of a Warrant or Warrants (represented by one or more
Warrant Certificates), and without payment of the Warrant Price in cash, for
such number of shares as shall be equal to the product of (1) the number of
shares for which such Warrant is exercisable with payment in cash of the Warrant
Price as of the date of exercise multiplied by (2) the Cashless Exercise Ratio
                                 -------------
or (iii) by any combination of (i) and (ii).  For purposes of this Agreement,
the "Cashless Exercise Ratio" shall equal a fraction, the numerator of which is
the excess of the Current Market Price per share of the Common Stock on the date
of exercise over the Warrant Price per share as of the date of exercise and the
denominator of which is the Current Market Price per share of the Common Stock
on the date of exercise.  An exercise of a Warrant in accordance with the
immediately preceding sentences is herein called a "Cashless Exercise."  Upon
surrender of a Warrant Certificate representing more than one Warrant in
connection with the Holder's option to elect a Cashless Exercise, the number of
shares deliverable upon a Cashless Exercise shall be equal to the Cashless
Exercise Ratio multiplied by the number of Warrants that the Holder specifies is
to be exercised pursuant to a Cashless Exercise.  All provisions of this
Agreement shall be applicable with respect to an exercise of a Warrant
Certificate pursuant to a Cashless Exercise for less than the full number of
Warrants represented thereby.

Payment of Taxes and Charges
----------------------------

          All shares of Common Stock issuable upon the exercise of this Warrant
pursuant to the terms hereof shall be validly issued, fully paid and
nonassessable, without any preemptive rights.  The Company shall pay all
expenses in connection with, and all taxes and other governmental charges that
may be imposed with respect to, the issue or delivery thereof, unless such tax
or charge is imposed by law upon Holder, in which case such taxes or charges
shall be paid by Holder.  The Company shall not be required, however, to pay any
tax or other charge imposed in connection with any transfer involved in the
issue of any certificate for shares of Common Stock issuable upon exercise of
this Warrant in any name other than that of Holder, and in such case the Company
shall not be required to issue or deliver any stock certificate until such tax
or other charge has been paid or it has been established to the satisfaction of
the Company that no such tax or other charge is due.

Fractional Shares
-----------------

          The Company shall not be required to issue a fractional share of
Common Stock upon exercise of any Warrant.  As to any fraction of a share which
Holder would otherwise be entitled to purchase upon such exercise, the Company
shall pay a cash adjustment in respect of such final fraction in an amount equal
to the same fraction of the Market Price per share of Common Stock as of the
Closing Date.

Continued Validity
------------------

          A holder of shares of Common Stock issued upon the exercise of this
Warrant, in whole or in part (other than a holder who acquires such shares after
the same have been publicly sold pursuant to a Registration Statement under the
Securities Act or sold pursuant to Rule 144 thereunder), shall continue to be
entitled with

                                      71
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respect to such shares to all rights to which it would have been entitled as
Holder under Sections 9, 10 and 14 of this Warrant. The Company will, at the
time of exercise of this Warrant, in whole or in part, upon the request of
Holder, acknowledge in writing, in form reasonably satisfactory to Holder, its
continuing obligation to afford Holder all such rights; provided, however, that
if Holder shall fail to make any such request, such failure shall not affect the
continuing obligation of the Company to afford to Holder all such rights to the
extent permitted by law.

                      Transfer, Division and Combination
                      ----------------------------------
Transfer
--------

          Subject to compliance with Section 9, transfer of this Warrant and all
rights hereunder, in whole or in part, shall be registered on the books of the
Company to be maintained for such purpose, upon surrender of this Warrant at the
principal office of the Company referred to in Section 2.1 or the office or
agency designated by the Company pursuant to Section 12, together with a written
assignment of this Warrant substantially in the form of Exhibit B hereto duly
executed by Holder or its agent or attorney and funds sufficient to pay any
transfer taxes payable upon the making of such transfer.  Upon such surrender
and, if required, such payment, the Company shall, subject to Section 9, execute
and deliver a new Warrant or Warrants in the name of the assignee or assignees
and in the denomination specified in such instrument of assignment, and shall
issue to the assignor a new Warrant evidencing the portion of this Warrant not
so assigned, and this Warrant shall promptly be canceled.  A Warrant, if
properly assigned in compliance with Section 9, may be exercised by a new Holder
for the purchase of shares of Common Stock without having a new warrant issued.

Division and Combination
------------------------

          Subject to Section 9, this Warrant may be divided or combined with
other Warrants upon presentation hereof at the aforesaid office or agency of the
Company, together with a written notice specifying the names and denominations
in which new Warrants are to be issued, signed by Holder or its agent or
attorney.  Subject to compliance with Section 3.1 and with Section 9, as to any
transfer which may be involved in such division or combination, the Company
shall execute and deliver a new Warrant or Warrants in exchange for the Warrant
or Warrants to be divided or combined in accordance with such notice.

Expenses
--------

          The Company shall prepare, issue and deliver at its own expense (other
than transfer taxes) the new Warrants or Warrants under this Section 3.

Maintenance of Books
--------------------

          The Company agrees to maintain, at its aforesaid office or agency,
books for the registration and the registration of transfer of the Warrants.

                                  Adjustments
                                  -----------

          The number of shares of Common Stock for which this Warrant is
exercisable, or the price at which such shares may be purchased upon exercise of
this Warrant, shall be subject to adjustment from time to time as set forth in
this Section 4. The Company shall give Holder notice of any event described
below which requires an adjustment pursuant to this Section 4 at the time of
such event.

Stock Dividends, Subdivisions and Combinations
----------------------------------------------

          If at any time the Company shall:
  take a record of the holders of its Common Stock for the purpose of entitling
  them to receive a dividend
   payable in, or other distribution of, Additional Shares of Common Stock;
  subdivide its outstanding shares of Common Stock into a larger number of
  shares of Common Stock; or
   combine its outstanding shares of Common Stock into a smaller number of
   shares of Common Stock;

then (i) the number of shares of Common Stock for which this Warrant is
exercisable immediately after the occurrence of any such event shall be adjusted
to equal the number of shares of Common Stock which a record holder of the same
number of shares of Common Stock for which this Warrant is exercisable
immediately prior to the occurrence of such event would own or be entitled to
receive after the happening of such event, and (ii) the Current Warrant Price
shall be adjusted to equal (A) the Current Warrant Price multiplied by the
number of shares of Common Stock for which this Warrant is exercisable
immediately prior to the adjustment divided by (B) the number of shares for
which this Warrant is exercisable immediately after such adjustment.

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Certain Other Distributions
---------------------------

          If at any time the Company shall take a record of the holders of its
Common Stock for the purpose of entitling them to receive any dividend or other
distribution of:
                                    cash;
    any evidences of its indebtedness, any shares of its stock or any other
 securities or property of any nature whatsoever (other than cash, Convertible
               Securities or Additional Shares of Common Stock);
 or any warrants or other rights to subscribe for or purchase any evidences of
its indebtedness, any shares of its stock or any other securities or property of
 any nature whatsoever (other than cash, Convertible Securities or Additional
                           Shares of Common Stock);

then Holder shall be entitled to receive such dividend or distribution as if
Holder had exercised the Warrant.  A reclassification of the Common Stock (other
than a change in par value, or from par value to no par value or from no par
value to par value) into shares of Common Stock and shares of any other class of
stock shall be deemed a distribution by the Company to the holders of its Common
Stock of such shares of such other class of stock within the meaning of this
Section 4.2 and, if the outstanding shares of Common Stock shall be changed into
a larger or smaller number of shares of Common Stock as a part of such
reclassification, such change shall be deemed a subdivision or combination, as
the case may be, of the outstanding shares of Common Stock within the meaning of
Section 4.1.

Other Provisions Applicable to Adjustments under this Section
-------------------------------------------------------------

          The following provisions shall be applicable to the making of
adjustments of the number of shares of Common Stock for which this Warrant is
exercisable and the Current Warrant Price provided for in this Section 4:

When Adjustments to be Made. The adjustments required by this Section 4 shall be
made whenever and as often as any specified event requiring an adjustment shall
occur. For the purpose of any adjustment, any specified event shall be deemed to
     have occurred at the close of business on the date of its occurrence.

     Fractional Interests.  In computing adjustments under this Section 4,
fractional interests in Common Stock shall be taken into account to the nearest
                              1/10th of a share.

When Adjustment not Required. If the Company shall take a record of the holders
of its Common Stock for the purpose of entitling them to receive a dividend or
distribution or subscription or purchase rights and shall, thereafter and before
 the distribution to stockholders thereof, legally abandon its plan to pay or
  deliver such dividend, distribution, subscription or purchase rights, then
  thereafter no adjustment shall be required by reason of the taking of such
  record and any such adjustment previously made in respect thereof shall be
                            rescinded and annulled.

 Challenge to Good Faith Determination. Whenever the Board of Directors of the
  Company shall be required to make a determination in good faith of the fair
value of any item under this Section 4, such determination may be challenged in
 good faith by the Holder, and any dispute shall be resolved by an investment
   banking firm of recognized national standing selected by the Company and
                             acceptable to Holder.

Reorganization, Reclassification, Merger, Consolidation or Disposition of Assets
--------------------------------------------------------------------------------

          In case the Company shall reorganize its capital, reclassify its
capital stock, consolidate or merge with or into another corporation (where the
Company is not the surviving corporation or where there is a change in or
distribution with respect to the Common Stock of the Company), or sell, transfer
or otherwise dispose of all or substantially all its property, assets or
business to another corporation and, pursuant to the terms of such
reorganization, reclassification, merger, consolidation or disposition of
assets, shares of common stock of the successor or acquiring corporation, or any
cash, shares of stock or other securities or property of any nature whatsoever
(including warrants or other subscription or purchase rights) in addition to or
in lieu of common stock of the successor or acquiring corporation ("Other
Property"), are to be received by or distributed to the holders of Common Stock
of the Company, then Holder shall have the right thereafter to receive, upon
exercise of the Warrant, the number of shares of common stock of the successor
or acquiring corporation or of the Company, if it is the surviving corporation,
and Other Property receivable upon or as a result of such reorganization,
reclassification, consolidation or disposition of assets by a holder of the
number of shares of Common Stock for which this Warrant is exercisable
immediately prior to such event.  In case of any such reorganization,
reclassification, merger, consolidation or disposition of assets, the successor
or acquiring corporation (if other than the Company) shall expressly assume the
due and punctual observance and performance of each and every covenant and
condition of

                                      73
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this Warrant to be performed and observed by the Company and all the obligations
and liabilities hereunder, subject to such modifications as may be deemed
appropriate (as determined by resolution of the Board of Directors of the
Company) in order to provide for adjustments of shares of Common Stock for which
this Warrant is exercisable which shall be as nearly equivalent as practicable
to the adjustments provided for in this Section 4. For purposes of this Section
4.4, "common stock of the successor or acquiring corporation" shall include
stock of such corporation of any class which is not preferred as to dividends or
assets over any other class of stock of such corporation and which is not
subject to redemption and shall also include any evidences of indebtedness,
shares of stock or other securities which are convertible into or exchangeable
for any such stock, either immediately or upon the arrival of a specified date
or the happening of a specified event and any warrants or other rights to
subscribe for or purchase any such stock. The foregoing provisions of this
Section 4.4 still similarly apply to successive reorganizations,
reclassifications, mergers, consolidations or disposition of assets.

Other Action Affecting Common Stock
-----------------------------------

          In case at any time or from time to time the Company shall take any
action in respect of its Common Stock, other than any action described in this
Section 4, which would have a materially adverse effect upon the rights of
Holder, the number of shares of Common Stock and/or the purchase price thereof
shall be adjusted in such manner as may be equitable in the circumstances, as
determined in good faith by the Board of Directors of the Company.

Certain Limitations
-------------------

          Notwithstanding anything herein to the contrary, the Company agrees
not to enter into any transaction which, by reason of any adjustment hereunder,
would cause the Current Warrant Price to be less than the par value per share of
Common Stock.

                               Notices to Holder
                               -----------------
Notice of Adjustments
---------------------

          Whenever the number of shares of Common Stock for which this Warrant
is exercisable, or whenever the price at which a share of such Common Stock may
be purchased upon exercise of the Warrants, shall be adjusted pursuant to
Section 4, the Company shall forthwith prepare a certificate to be executed by
the chief financial officer of the Company setting forth, in reasonable detail,
the event requiring the adjustment and the method by which such adjustment was
calculated (including a description of the basis on which the Board of Directors
of the Company determined the fair value of any evidences of indebtedness,
shares of stock, other securities or property or warrants or other subscription
or purchase rights referred to in Section 4.2), specifying the number of shares
of Common Stock for which this Warrant is exercisable and (if such adjustment
was made pursuant to Section 4.4 or 4.5) describing the number and kind of any
other shares of stock or Other Property for which this Warrant is exercisable,
and any change in the purchase price or prices thereof, after giving effect to
such adjustment or change.  The Company shall promptly cause a signed copy of
such certificate to be delivered to the Holder in accordance with Section 14.2.
The Company shall keep at its office or agency designated pursuant to Section 12
copies of all such certificates and cause the same to be available for
inspection at said office during normal business hours by the Holder or any
prospective purchaser of a Warrant designated by Holder.

Notice of Corporate Action
--------------------------

          If at any time:
  the Company shall take a record of the holders of its Common Stock for the
 purpose of entitling them to receive a dividend or other distribution, or any
right to subscribe for or purchase any evidences of its indebtedness, any shares
 of stock of any class or any other securities or property, or to receive any
                                other right; or
there shall be any capital reorganization of the Company, any reclassification
or recapitalization of the capital stock of the Company or any consolidation or
merger of the Company with, or any sale, transfer or other disposition of all or
 substantially all the property, assets or business of the Company to, another
                                corporation; or
there shall be a voluntary or involuntary dissolution, liquidation or winding up
                                of the Company;

then, in any one or more of such cases, the Company shall give to Holder (i) at
least 30 days' prior written notice of the date on which a record date shall be
selected for such dividend, distribution or right or for determining rights to
vote in respect of any such reorganization, reclassification, merger,
consolidation, sale, transfer, disposition,

                                      74
<PAGE>

dissolution, liquidation or winding up, and (ii) in the case of any such
reorganization, reclassification, merger, consolidation, sale, transfer,
disposition, dissolution, liquidation or winding up, at least 30 days' prior
written notice of the date when the same shall take place. Such notice in
accordance with the foregoing clause also shall specify (i) the date on which
any such record is to be taken for the purpose of such dividend, distribution or
right, the date on which the holders of Common Stock shall be entitled to any
such dividend, distribution or right, and the amount and character thereof, and
(ii) the date on which any such reorganization, reclassification, merger,
consolidation, sale, transfer, disposition, dissolution, liquidation or winding
up is to take place and the time, if any such time is to be fixed, as of which
the holders of Common Stock shall be entitled to exchange their shares of Common
Stock for securities or other property deliverable upon such reorganization,
reclassification, merger, consolidation, sale, transfer, disposition,
dissolution, liquidation or winding up. Each such written notice shall be
sufficiently given if addressed to Holder at the last address of Holder
appearing on the books of the Company and delivered in accordance with Section
14.2.

                                 No Impairment
                                 -------------

          The Company shall not by any action, including, without limitation,
amending its certificate of incorporation or through any reorganization,
transfer of assets, consolidation, merger, dissolution, issue or sale of
securities or other voluntary action, avoid or seek to avoid the observance or
performance of any of the terms of this Warrant, but will at all times in good
faith assist in the carrying out of all such terms and in the taking of all such
actions as may be necessary or appropriate to protect the rights of Holder
against impairment.  Without limiting the generality of the foregoing, the
Company will (a) not increase the par value of any shares of Common Stock
receivable upon the exercise of this Warrant above the amount payable therefor
upon such exercise immediately prior to such increase in par value, (b) take all
such action as may be necessary or appropriate in order that the Company may
validly and legally issue fully paid and nonassessable shares of Common Stock
upon the exercise of this Warrant, and (c) use its best efforts to obtain all
such authorizations, exemptions or consents from any public regulatory body
having jurisdiction thereof as may be necessary to enable the Company to perform
its obligations under this Warrant.

          Upon the request of Holder, the Company will at any time during the
period this Warrant is outstanding acknowledge in writing, in form satisfactory
to Holder, the continuing validity of this Warrant and the obligations of the
Company hereunder, to the extent permitted by law.

                 Reservation and Authorization of Common Stock
                 ---------------------------------------------

          From and after the Closing Date, the Company shall at all times
reserve and keep available for issue upon the exercise of Warrants such number
of its authorized but unissued shares of Common Stock as will be sufficient to
permit the exercise in full of all outstanding Warrants.  All shares of Common
Stock which shall be so issuable, when issued upon exercise of any Warrant and
payment therefor in accordance with the terms of such Warrant, shall be duly and
validly issued and fully paid and nonassessable and not subject to preemptive
rights.

          Before taking any action which would cause an adjustment reducing the
Current Warrant Price below the then par value, if any, of the shares of Common
Stock issuable upon exercise of the Warrants, the Company shall take any
corporate action which may be necessary in order that the Company may validly
and legally issue fully paid and nonassessable shares of such Common Stock at
such adjusted Current Warrant Price.

          Before taking any action which would result in an adjustment in the
number of shares of Common Stock for which this Warrant is exercisable or in the
Current Warrant Price, the Company shall obtain all such authorizations or
exemptions thereof, or consents thereto, as may be necessary from any public
regulatory body or bodies having jurisdiction thereof.

              Taking of Record; Stock and Warrant Transfer Books
              --------------------------------------------------

          In the case of all dividends or other distributions by the Company to
the holders of its Common Stock with respect to which any provision of Section 4
refers to the taking of record of such holders, the Company will in each case
take such a record and will take such record as of the close of business on a
Business Day.  The Company will not at any time, except upon dissolution,
liquidation or winding up of the Company, close its stock transfer books or
Warrant transfer books so as to result in preventing or delaying the exercise or
transfer of any Warrant.

                                 75
<PAGE>

                        Restrictions on Transferability
                        -------------------------------

          The Warrants and the Warrant Stock shall not be transferred,
hypothecated or assigned before satisfaction of the conditions specified in this
Section 9, which conditions are intended to ensure compliance with the
provisions of the Securities Act with respect to the Transfer of any Warrant or
any Warrant Stock.  Holder, by acceptance of this Warrant, agrees to be bound by
the provisions of this Section 9.

Restrictive Legend
------------------

Holder, by accepting this Warrant and any Warrant Stock agrees that this Warrant
and the Warrant Stock issuable upon exercise hereof may not be assigned or
otherwise transferred unless and until (i) the Company has received an opinion
of counsel for Holder that such securities may be sold pursuant to an exemption
from registration under the Securities Act or (ii) a registration statement
relating to such securities has been filed by the Company and declared effective
by the Commission.

          Each certificate for Warrant Stock issuable hereunder shall bear a
legend as follows until such securities have been sold pursuant to an effective
registration statement under the Securities Act:

          "THESE SECURITIES HAVE NOT BEEN REGISTERED UNDER THE
          SECURITIES ACT OF 1933, AS AMENDED (THE "SECURITIES ACT"),
          OR THE SECURITIES LAWS OF ANY STATE, AND ARE BEING OFFERED
          AND SOLD PURSUANT TO AN EXEMPTION FROM THE REGISTRATION
          REQUIREMENTS OF THE SECURITIES ACT AND SUCH LAWS. THESE
          SECURITIES MAY NOT BE SOLD OR TRANSFERRED EXCEPT PURSUANT TO
          AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT
          OR PURSUANT TO AN AVAILABLE EXEMPTION FROM THE REGISTRATION
          REQUIREMENTS OF THE SECURITIES ACT OR SUCH OTHER LAWS."

Except as otherwise provided in this Section 9, the Warrant shall be stamped or
otherwise imprinted with a legend in substantially the following form:

          "THIS WARRANT AND THE SECURITIES REPRESENTED HEREBY HAVE NOT
          BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
          AMENDED, AND MAY NOT BE TRANSFERRED IN VIOLATION OF SUCH
          ACT, THE RULES AND REGULATIONS THEREUNDER OR THE PROVISIONS
          OF THIS WARRANT."

Notice of Proposed Transfers
----------------------------

          Prior to any Transfer or attempted Transfer of any Warrants or any
shares of Restricted Common Stock, the Holder shall give ten days' prior written
notice (a "Transfer Notice") to the Company of Holder's intention to effect such
Transfer, describing the manner and circumstances of the proposed Transfer, and
obtain from counsel to Holder who shall be reasonably satisfactory to the
Company, an opinion that the proposed Transfer of such Warrants or such
Restricted Common Stock may be effected without registration under the
Securities Act.  After receipt of the Transfer Notice and opinion, the Company
shall, within five days thereof, notify the Holder as to whether such opinion is
reasonably satisfactory and, if so, such holder shall thereupon be entitled to
Transfer such Warrants or such Restricted Common Stock, in accordance with the
terms of the Transfer Notice.  Each certificate, if any, evidencing such shares
of Restricted Common Stock issued upon such Transfer shall bear the restrictive
legend set forth in Section 9.1(a), and the Warrant issued upon such Transfer
shall bear the restrictive legend set forth in Section 9.1(b), unless in the
opinion of such counsel such legend is not required in order to ensure
compliance with the Securities Act.  Holder shall not be entitled to Transfer
such Warrants or such Restricted Common Stock until receipt of notice from the
Company under this Section 9.2(a) that such opinion is reasonably satisfactory.

Required Registration
---------------------

          Pursuant to the terms and conditions set forth in Registration Rights
Agreement, the Company shall prepare and file with the Commission not later than
April 1, 2000, a Registration Statement relating to the offer and sale of the
Common Stock issuable upon exercise of the Warrants and shall use its best
efforts to cause the

                                 76
<PAGE>

Commission to declare such Registration Statement effective under the Securities
Act as promptly as practicable but no later than June 1, 2000.

Termination of Restrictions
---------------------------

          Notwithstanding the foregoing provisions of Section 9, the
restrictions imposed by this Section upon the transferability of the Warrants,
the Warrant Stock and the Restricted Common Stock (or Common Stock issuable upon
the exercise of the Warrants) and the legend requirements of Section 9.1 shall
terminate as to any particular Warrant or share of Warrant Stock or Restricted
Common Stock (or Common Stock issuable upon the exercise of the Warrants) (i)
when and so long as such security shall have been effectively registered under
the Securities Act and disposed of pursuant thereto or (ii) when the Company
shall have received an opinion of counsel reasonably satisfactory to it that
such shares may be transferred without registration thereof under the Securities
Act.  Whenever the restrictions imposed by Section 9 shall terminate as to this
Warrant, as hereinabove provided, the Holder hereof shall be entitled to receive
from the Company upon written request of the Holder, at the expense of the
Company, a new Warrant bearing the following legend in place of the restrictive
legend set forth hereon:

          "THE RESTRICTIONS ON TRANSFERABILITY OF THE WITHIN WARRANT
          CONTAINED IN SECTION 9 HEREOF TERMINATED ON __________,
          _____, AND ARE OF NO FURTHER FORCE AND EFFECT."

All Warrants issued upon registration of transfer, division or combination of,
or in substitution for, any Warrant or Warrants entitled to bear such legend
shall have a similar legend endorsed thereon.  Whenever the restrictions imposed
by this Section shall terminate as to any share of Restricted Common Stock, as
hereinabove provided, the holder thereof shall be entitled to receive from the
Company, at the Company's expense, a new certificate representing such Common
Stock not bearing the restrictive legend set forth in Section 9.1(a).

Listing on Securities Exchange
------------------------------

          If the Company shall list any shares of Common Stock on any securities
exchange or quotation system, it will, at its expense, list thereon, maintain
and, when necessary, increase such listing of, all shares of Common Stock issued
or, to the extent permissible under the applicable securities exchange rules,
issuable upon the exercise of this Warrant so long as any shares of Common Stock
shall be so listed during any such Exercise Period.

                             Supplying Information
                             ---------------------

          The Company shall cooperate with Holder in supplying such information
as may be reasonably necessary for Holder to complete and file any information
reporting forms presently or hereafter required by the Commission as a condition
to the availability of an exemption from the Securities Act for the sale of any
Warrant or Restricted Common Stock.

                              Loss or Mutilation
                              ------------------

          Upon receipt by the Company from Holder of evidence reasonably
satisfactory to it of the ownership of and the loss, theft, destruction or
mutilation of this Warrant and indemnity reasonably satisfactory to it (it being
understood that the written agreement of the Holder shall be sufficient
indemnity), and in case of mutilation upon surrender and cancellation hereof,
the Company will execute and deliver in lieu hereof a new Warrant of like tenor
to Holder; provided, in the case of mutilation no indemnity shall be required if
this Warrant in identifiable form is surrendered to the Company for
cancellation.

                             Office of the Company
                             ---------------------

          As long as any of the Warrants remain outstanding, the Company shall
maintain an office or agency (which may be the principal executive offices of
the Company) where the Warrants may be presented for exercise, registration of
transfer, division or combination as provided in this Warrant.

                            Limitation of Liability
                            -----------------------

          No provision hereof, in the absence of affirmative action by Holder to
purchase shares of Common Stock, and no enumeration herein of the rights or
privileges of Holder hereof, shall give rise to any liability of Holder for the
purchase price of any Common Stock or as a stockholder of the Company, whether
such liability is asserted by the Company or by creditors of the Company.

                                      77
<PAGE>

                                 Miscellaneous
                                 -------------
Nonwaiver and Expenses
----------------------

          No course of dealing or any delay or failure to exercise any right
hereunder on the part of Holder shall operate as a waiver of such right or
otherwise prejudice Holder's rights, powers or remedies.  If the Company fails
to make, when due, any payments provided for hereunder, or fails to comply with
any other provision of this Warrant, the Company shall pay to Holder such
amounts as shall be sufficient to cover any costs and expenses including,
without limitation, reasonable attorneys' fees, including those of appellate
proceedings, incurred by Holder in collecting any amounts due pursuant hereto or
in otherwise enforcing any of its rights, powers or remedies hereunder.

Notice Generally
----------------

          Except as may be otherwise provided herein, any notice or other
communication or delivery required or permitted hereunder shall be in writing
and shall be delivered personally or sent by certified mail, postage prepaid, or
by a nationally recognized overnight courier service, and shall be deemed given
when so delivered personally or by overnight courier service, or, if mailed,
three days after the date of deposit in the United States mails, as follows:

                            if to the Company, to:

               American TeleSource International, Inc.
               12500 Network Boulevard, Suite 407
               San Antonio, Texas  78249
               (210) 558-6090
               (210) 558-6095 (Fax)
               Attention: H. Douglas Saathoff

               with a copy to:

               Alice L. King, Esq.
               Corporate Counsel
               American TeleSource International, Inc.
               12500 Network Boulevard, Suite 407
               San Antonio, Texas 78249
               (210) 558-6090
               (210) 558-6095 (Fax)

                            if to the Holder, to:

               The Shaar Fund Ltd.,
               c/o Levinson Capital Management
               2 World Trade Center, Suite 1820
               New York, NY 10048
               Attention: Samuel Levinson
               (212) 432-7771
               (212) 432-7771 (Fax)

               with a copy to:

               Cadwalader, Wickersham & Taft
               100 Maiden Lane
               New York, NY 10038
               Attention: Dennis J. Block, Esq.
               (212) 504-5555
               (212) 504-5557 (Fax)

The Company or the Holder may change the foregoing address by notice given
pursuant to this Section 14.2.

                                      78
<PAGE>

Indemnification
---------------

          The Company agrees to indemnify and hold harmless Holder from and
against any liabilities, obligations, losses, damages, penalties, actions,
judgments, suits, claims, costs, attorneys' fees, expenses and disbursements of
any kind (collectively, "Losses") which may be imposed upon, incurred by or
asserted against Holder in any manner relating to or arising out of any failure
by the Company to perform or observe in any material respect any of its
covenants, agreements, undertakings or obligations set forth in this Warrant;
provided, however, that the Company shall not be liable under this Section 14.3
to the extent that any liabilities, obligations, losses, damages, penalties,
actions, judgments, suits, claims, costs, attorneys' fees, expenses or
disbursements are found in a final nonappealable judgment by a court to have
resulted from Holder's gross negligence, bad faith or willful misconduct in its
capacity as a stockholder or warrantholder of the Company; and provided,
further, that the Company shall not be liable under this Section 14.3 to the
extent that it has provided indemnity to Holder with respect to any Losses
pursuant to the Registration Rights Agreement.

Remedies
--------

          Holder in addition to being entitled to exercise all rights granted by
law, including recovery of damages, will be entitled to specific performance of
its rights under Section 9 of this Warrant.  The Company agrees that monetary
damages would not be adequate compensation for any loss incurred by reason of a
breach by it of the provisions of Section 9 of this Warrant and hereby agrees to
waive the defense in any action for specific performance that a remedy at law
would be adequate.

Successors and Assigns
----------------------

          Subject to the provisions of Sections 3.1 and 9, this Warrant and the
rights evidenced hereby shall inure to the benefit of and be binding upon the
successors of the Company and the successors and assigns of Holder.  The
provisions of this Warrant are intended to be for the benefit of all Holders
from time to time of this Warrant and, with respect to Section 9 hereof, holders
of Warrant Stock, and shall be enforceable by any such Holder or holder of
Warrant Stock.

Amendment
---------

          This Warrant and all other Warrants may be modified or amended or the
provisions hereof waived with the written consent of the Company and Holder.

Severability
------------

          Wherever possible, each provision of this Warrant shall be interpreted
in such manner as to be effective and valid under applicable law, but if any
provision of this Warrant shall be prohibited by or invalid under applicable
law, such provision shall only be ineffective to the extent of such prohibition
or invalidity, without invalidating the remainder of such provision or the
remaining provisions of this Warrant.

Headings
--------

          The headings used in this Warrant are for the convenience of reference
only and shall not, for any purpose, be deemed a part of this Warrant.

Governing Law
-------------

          This Warrant shall be governed by the laws of the State of New York,
without regard to the provisions thereof relating to conflicts of law.

                        [NO FURTHER TEXT ON THIS PAGE]

                                      79
<PAGE>

          In Witness Whereof, the Company has caused this Warrant to be duly
executed and its corporate seal to be impressed hereon and attested by its
Secretary or an Assistant Secretary.

Dated:  February __, 2000

                                 American TeleSource International, Inc.

                                 By:_____________________________________
                                    Name:  H. Douglas Saathoff
                                    Title: Chief Financial Officer

Attest:

By:______________________________
   Name:
   Title:

                                      80
<PAGE>

                                                                       EXHIBIT A

                               SUBSCRIPTION FORM

                [To be executed only upon exercise of Warrant]

          The undersigned registered owner of this Warrant irrevocably exercises
this Warrant for the purchase of __________ shares of Common Stock of American
TeleSource International, Inc. and herewith makes payment therefor, all at the
price and on the terms and conditions specified in this Warrant and requests
that certificates for the shares of Common Stock hereby purchased (and any
securities or other property issuable upon such exercise) be issued in the name
of and delivered to

________________________________________________________________________________
whose address is

________________________________________________________________________________

and, if such shares of Common Stock shall not include all of the shares of
Common Stock issuable as provided in this Warrant, that a new Warrant of like
tenor and date for the balance of the shares of Common Stock issuable hereunder
be delivered to the undersigned.


                                        ________________________________________
                                               (Name of Registered Owner)

                                         _______________________________________
                                             (Signature of Registered Owner)

                                        ________________________________________
                                                    (Street Address)

                                        ________________________________________
                                        (City)         (State)        (Zip Code)

                                        Notice: The signature on this
                                        subscription must correspond with the
                                        name as written upon the face of the
                                        within Warrant in every particular,
                                        without alteration or enlargement or any
                                        change whatsoever.

                                      81
<PAGE>

                                                                       EXHIBIT B

                                ASSIGNMENT FORM

          For Value Received the undersigned registered owner of this Warrant
hereby sells, assigns and transfers unto the Assignee named below all of the
rights of the undersigned under this Warrant, with respect to the number of
shares of Common Stock set forth below:

                                                       No. of Shares of
     Name and Address of Assignee                         Common Stock
     ----------------------------                         ------------



and does hereby irrevocably constitute and appoint

________________________________________________________________________________

attorney-in-fact to register such transfer on the books of American TeleSource
International, Inc. maintained for the purpose, with full power of substitution
in the premises.

Dated: ________________________


                                        ________________________________________
                                                       (Print Name)

                                        ________________________________________
                                                        (Signature)

                                        ________________________________________
                                                  (Print Name of Witness)

                                        ________________________________________
                                                   (Witness's Signature)

                                        Notice: The signature on this assignment
                                        must correspond with the name as written
                                        upon the face of the within Warrant in
                                        every particular, without alteration or
                                        enlargement or any change whatsoever.

                                      82