<PAGE>

                                                                   EXHIBIT 4.20

THIS COMMON STOCK PURCHASE WARRANT HAS NOT BEEN REGISTERED UNDER THE SECURITIES
ACT OF 1933, AS AMENDED (THE "SECURITIES ACT") OR UNDER ANY APPLICABLE LAW OR
REGULATION OF ANY STATE.  THIS COMMON STOCK WARRANT MAY NOT BE SOLD, OFFERED,
ASSIGNED OR TRANSFERRED UNLESS THE WARRANT IS REGISTERED UNDER THE SECURITIES
ACT AND APPLICABLE STATE SECURITIES LAWS, OR UNLESS SUCH OFFERS, SALES,
ASSIGNMENTS AND TRANSFERS ARE MADE PURSUANT TO THE AVAILABLE EXEMPTIONS FROM THE
REGISTRATION REQUIREMENTS OF THOSE LAWS.

                      DIAL-THRU INTERNATIONAL CORPORATION

                              AMENDED AND RESTATED
                         COMMON STOCK PURCHASE WARRANT
                                    (No. 2)

                                                           DATED:  March 1, 2000

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Number of Common Shares:      50,000                 Holder: Juan Carlos Gaviria
Purchase Price:               $.88
Expiration Date:              Two (2) years from date of vesting

               For identification only. The governing terms of
                       this Warrant are set forth below.
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     DIAL-THRU INTERNATIONAL CORPORATION, a Delaware corporation (the
"Company"), hereby certifies that, for value received, Juan Carlos Gaviria (the
"Holder") is entitled, subject to the terms set forth below, to purchase from
the Company at any time or from time to time prior to two (2) years following
the date of vesting of the Warrant at the Purchase Price hereinafter set forth,
Fifty Thousand (50,000) fully paid and nonassessable shares of Common Stock (as
defined below) of the Company.  This Warrant is being executed and delivered in
connection with the Distribution Agreement (as defined below), and modifies and
restates in its entirety the terms of the Common Stock Purchase Warrant dated
October 26, 1999 previously issued to LGIT, Inc.  The number and character of
such shares of Common Stock and the Purchase Price are subject to adjustment as
provided herein.

     The purchase price per share of Common Stock issuable upon exercise of
this Warrant (the "Purchase Price") shall initially be $.88, provided, however,
that the Purchase Price shall be adjusted from time to time as provided herein.

     As used herein the following terms, unless the context otherwise requires,
have the following respective meanings:

           (a)   The term "Company" means Dial-Thru International Corporation
     and any entity that shall succeed or assume the obligations of such
     corporation hereunder.

           (b)   The term "Common Stock" means the Company's common stock, .001
     par value per share.

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           (c)   The term "Consolidated Revenues" means the combined revenues
     of the Distribution Group from the sales of the Company's prepaid phone
     cards.

           (d)   The term "Distribution Agreement " means the Distribution
     Agreement of even date herewith between the Company and Holder.

           (e)   The term "Distribution Group" means the following independent
     distributors of the Company's prepaid phone cards: Juan Carlos Gaviria,
     Alvaro Restrepo, Paul Saunier, Eric Ifflen, Emilio Martinez, Carlos Bedoya
     and Alfredo Polo.

           (f)   The term "Tax Withholding Liability" means all federal and
     state income taxes, social security taxes and other taxes applicable to
     compensation income arising from the exercise of this Warrant required by
     applicable law to be withheld by the Company.

           (g)   The term "Warrant Shares" means as of any date during the
     Exercise Period, that number of shares of Common Stock which shall be
     exercisable (subject to any vesting requirements) by the Holder hereof
     pursuant to the terms of this Warrant.

     1.    Vesting and Exercise of Warrant; Resale Restrictions.

           1.1.  Vesting. Holder's right to purchase 50% (25,000) of the Warrant
     Shares shall vest immediately upon the execution and delivery of this
     Warrant and shall be immediately exercisable. Holder's right to purchase
     the remaining 50% (25,000) Warrant Shares hereunder shall vest upon the
     Distributor Group's achieving Consolidated Revenues of in excess of $10
     million for a period of three consecutive calendar months on or before
     February 28, 2002. Holder shall not have any right to acquire any Warrant
     Shares pursuant to this Warrant prior to the vesting of such rights as set
     forth in this Section 1.1. If the Distributor Group fails to achieve
     Consolidated Revenues of in excess of $10 million in three consecutive
     calendar months prior to February 28, 2002, then Holder's right to acquire
     the remaining 25,000 Warrant Shares pursuant to the terms of this Warrant
     shall fail to vest and Holder shall have no right to acquire such shares
     hereunder.

           1.2.  Method of Exercise. This Warrant may be exercised (subject to
     the vesting requirements set forth above) by the Holder hereof in whole or
     in part (but not as to a fractional share of Common Stock), at any time and
     from time to time during the Exercise Period for up to, but not more than,
     the number of vested Warrant Shares at such time, by delivery to the
     Company at its principal office of (i) a notice of exercise (a "Notice of
     Exercise") substantially in the form attached hereto as Exhibit A, (ii)
     evidence satisfactory to the Company of the authority of the person
     executing such Notice of Exercise, (iii) this Warrant, and (iv) payment of
     (A) the Purchase Price multiplied by the number of shares of Common Stock
     for which this Warrant is being exercised (the "Exercise Price") and (B)
     Tax Withholding Liability. Payment of the Exercise Price and Tax
     Withholding Liability shall be made by check or bank draft payable to the
     order of
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     the Company or by wire transfer to the account of the Company. The shares
     so purchased shall be deemed to be issued as of the close of business on
     the date on which the Company shall have received from the Holder payment
     in full of the Exercise Price and Tax Withholding Liability and the other
     documents referred to herein (the "Exercise Date"). Notwithstanding the
     foregoing, Holder shall not be entitled to exercise this Warrant, in whole
     or in part, unless and until Holder is current in all payment obligations
     to the Company, whether arising under the Distribution Agreement or
     otherwise.

           1.3.  Regulation D Restrictions. The Holder hereof represents and
     warrants to the Company that it has acquired this Warrant and anticipates
     acquiring the shares of Common Stock issuable upon exercise of the Warrant
     solely for its own account for investment purposes and not with a view to
     or for distributing such securities unless such distribution has been
     registered with the Securities and Exchange Commission or an applicable
     exemption is available therefor. At the time this Warrant is exercised, the
     Company may require the Holder to state in the Notice of Exercise such
     representations concerning the Holder as are necessary or appropriate to
     assure compliance by the Holder with the Securities Act.

           1.4.  Resale Restrictions. The Holder hereof covenants and agrees
     with the Company that it will not, without the prior written consent of the
     Company, sell more than 5,000 shares per month during the two-year period
     following any exercise of this Warrant by Holder.

     2.    Delivery of Stock Certificates, etc., on Exercise. As soon as
practicable after the exercise of this Warrant, the Company will cause to be
issued in the name of and delivered to the Holder a certificate for the number
of fully paid and nonassessable shares of Common Stock to which the Holder shall
be entitled on such exercise, plus, in lieu of any fractional share to which the
Holder would otherwise be entitled, cash equal to such fraction multiplied by
the then applicable Purchase Price, together with any other stock or other
securities and property (including cash, where applicable) to which the Holder
is entitled upon such exercise pursuant to Section 1 or otherwise.

     3.    Adjustments on Certain Capital Transactions. On the occurrence of any
of the following events, the following adjustments to the rights granted under
this Warrant shall be made:

           3.1.  In case the number of outstanding shares of Common Stock of the
     Company shall be increased by way of a stock dividend, stock split,
     recapitalization, or other similar means, the number of unexercised shares
     of Common Stock covered by this Warrant shall be increased by the amount
     that a like number of shares of outstanding Common Stock shall have been
     increased as a result of such stock increase and the Purchase Price shall
     be adjusted by multiplying the Purchase Price in effect immediately prior
     to such stock increase by a fraction, the numerator of which shall be the
     number of unexercised shares covered by this Warrant immediately prior to
     such stock increase and the denominator of which shall be the number of
     unexercised shares of Common Stock covered by this Warrant as adjusted for
     such stock increase.

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COMMON STOCK PURCHASE WARRANT - Page 3    (Dial-Thru International Corporation)
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           3.2.  In case the number of outstanding shares of Common Stock of the
     Company shall be reduced by recapitalization, reverse stock split or
     otherwise, the number of unexercised shares covered by this Warrant shall
     be reduced by the amount that a like number of shares of outstanding Common
     Stock shall have been reduced as a result of such stock reduction and the
     Purchase Price shall be adjusted by multiplying the Purchase Price in
     effect immediately prior to such stock reduction by a fraction, the
     numerator of which shall be the number of unexercised shares covered by
     this Warrant immediately prior to such stock reduction and the denominator
     of which shall be the number of unexercised shares covered by this Warrant
     as adjusted for such stock reduction.

           3.3.  In case the Company shall consolidate with or merge into
     another corporation, the holder of this Warrant will thereafter receive,
     upon the exercise thereof in accordance with the terms of this Warrant, the
     securities or property to which the holder of the number of shares of
     Common Stock then deliverable upon the exercise of this Warrant would have
     been entitled upon such consolidation or merger ("Other Securities") and
     the Company shall take such steps in connection with such consolidation or
     merger as may be necessary to assure that the provisions hereof shall
     thereafter be applicable, as nearly as reasonably may be, in relation to
     any securities or property thereafter deliverable upon the exercise of this
     Warrant.

     4.    Rights as a Shareholder. Holder shall not have any rights as a
shareholder of the Company with respect to the shares subject to this Warrant.

     5.    Securities Law Requirements. Neither this Warrant nor the Warrant
Shares have been registered under the Securities Act or any state securities or
blue sky laws. Accordingly, upon (a) any transfer of this Warrant, any
transferee of this Warrant or (b) the exercise of this Warrant in whole or in
part, and if the Warrant Shares have not been registered under the Securities
Act, Holder or any other person exercising this Warrant shall, as applicable,
represent and agree in writing satisfactory to the Company that Holder or such
other person (a) is acquiring the shares for the purpose of investment and not
with a view to distribution thereof, (b) knows the shares have not been
registered under the Securities Act or any state securities or blue sky laws,
(c) understands that he must bear the economic risk of said investment for an
indefinite period of time until the shares are registered under the Securities
Act and applicable state securities or blue sky laws or an exemption from such
registration is available, and (d) will not solicit any offer to sell or sell
all or any portion of the shares other than pursuant to an opinion of counsel
reasonably satisfactory to the Company.

     6.    Transfer Restrictions. This Warrant shall be exercisable only by
Holder and shall not be assignable or transferable. Any attempted alienation,
assignment, pledge, hypothecation, attachment, execution or similar process,
whether voluntary or involuntary, with respect to all or any part of this
Warrant or any right hereunder, shall be null and void.

     7.    Reservation of Stock, etc. Issuable on Exercise of Warrant. The
Company will at all times reserve and keep available, solely for issuance and
delivery on the exercise of this

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Warrant, all shares of Common Stock (or Other Securities) from time to time
issuable on the exercise of this Warrant.

     8.    Replacement of Warrant.  On receipt of evidence reasonably
satisfactory to the Company of the loss, theft, destruction or mutilation of
this Warrant and, in the case of any such loss, theft or destruction of this
Warrant, on delivery of an indemnity agreement or security satisfactory in form
and amount to the Company or, in the case of any such mutilation, on surrender
and cancellation of this Warrant, the Company at its expense will execute and
deliver, in lieu thereof, a new warrant of like tenor.

     9.    Notices, etc. All notices and other communications hereunder shall be
personally delivered, telecopied or mailed by first class registered or
certified mail, postage prepaid, at such address of facsimile numbers as may
have been furnished to each party by the other in writing.

     10.   Miscellaneous. This Warrant and any term hereof may be changed,
waived, discharged or terminated only by an instrument in writing signed by the
party against which enforcement of such change, waiver, discharge or termination
is sought. This Warrant shall be construed and enforced in accordance with and
governed by the internal laws of the State of Texas. The headings in this
Warrant are for purposes of reference only, and shall not limit or otherwise
affect any of the terms hereof. The invalidity or unenforceability of any
provision hereof shall in no way affect the validity or enforceability of any
other provision.

                           [SIGNATURE PAGE FOLLOWS]












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COMMON STOCK PURCHASE WARRANT - Page 5    (Dial-Thru International Corporation)
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     DATED as of March 1, 2000

                                        DIAL-THRU INTERNATIONAL CORPORATION



                                        By:       /s/ Roger D. Bryant
                                           --------------------------------
                                        Name:     Roger D. Bryant
                                             ------------------------------
                                        Title:    Chairman
                                              -----------------------------

                                        Address:  8100 Jetstar, Suite 100
                                                  Irving, Texas  75063
                                                  Fax: (972) 929-1616


                                        HOLDER:
                                        ------


                                        /s/ Juan Carlos Gaviria
                                        -----------------------------------
                                        Printed Name: Juan Carlos Gaviria


                                        Address:
                                                   ------------------------

                                                   ------------------------
                                                   Fax:
                                                       --------------------







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                                   EXHIBIT A

                     FORM OF NOTICE OF EXERCISE - WARRANT
                     ------------------------------------

               (To be executed only upon exercise or conversion
                      of the Warrant in whole or in part)

To Dial-Thru International Corporation

     The undersigned registered holder of the accompanying Warrant hereby
exercises such Warrant or portion thereof for, and purchases thereunder,
___________/20/ shares of Common Stock (as defined in such Warrant) and herewith
makes payment therefor (including any Tax Withholding Liability) of $__________,
as of the date written below. The undersigned requests that the certificates for
such shares of Common Stock be issued in the name of, and delivered to,
_______________________________________________ whose address is
_____________________________________________________________________________.



Dated:
      ---------------------------


                                        ---------------------------------------
                                        (Name must conform to name of Holder as
                                        specified on the face of the Warrant)



                                        By:
                                           ------------------------------------
                                        Name:
                                             ----------------------------------
                                        Title:
                                              ---------------------------------


                                        Address of Holder:

                                        ---------------------------------------

                                        ---------------------------------------

                                        ---------------------------------------


Date of exercise:
                 ---------------------




--------------------------
/20/  Insert the number of shares of Common Stock as to which the accompanying
Warrant is being exercised. In the case of a partial exercise, a new Warrant or
Warrants will be issued and delivered, representing the unexercised portion of
the accompanying Warrant, to the holder surrendering the same.