<PAGE>

                                                                     Exhibit 3.3

                     NETWORK ACCESS SOLUTIONS CORPORATION
       CERTIFICATE OF THE DESIGNATIONS, VOTING POWERS, PREFERENCES AND
                       RELATIVE, PARTICIPATING, OPTIONAL
                  OR OTHER SPECIAL RIGHTS OF PREFERRED STOCK
                      AND QUALIFICATIONS, LIMITATIONS OR
                             RESTRICTIONS THEREOF

               ________________________________________________

                         Pursuant to Section 151 of the
               General Corporation Law of the State of Delaware

               ________________________________________________

          We, the undersigned, being the President and Chief Executive Officer,
and the Secretary, respectively, of Network Access Solutions Corporation, a
Delaware corporation (the "Corporation"), DO HEREBY CERTIFY, pursuant to Section
151 of the General Corporation Law of the State of Delaware, that the following
resolution was duly adopted by the Board of Directors of the Corporation as of
February 4, 2000:

          "RESOLVED, that pursuant to the authority expressly granted to and
vested in the Board of Directors of the Corporation (the "Board of Directors")
by the provisions of the Amended and Restated Certificate of Incorporation of
the Corporation, the Board of Directors hereby creates and designates a series
of preferred stock of the Corporation to consist of one million five hundred
thousand (1,500,000) shares, each of $0.001 par value, and the Board of
Directors hereby fixes the relative rights and preferences of the shares of such
Series as follows:

          1.   Designation.  The shares of such series of preferred stock shall
               -----------
be designated "Series B Convertible Preferred Stock" (referred to herein as the
"Series B Preferred Stock") and shall be senior to all other capital stock of
the Corporation as to the distribution of assets on liquidation, dissolution and
winding up of the Corporation and with respect to dividends.

          2.   Authorized Number.  The number of shares constituting the Series
               -----------------
B Preferred Stock shall be one million five hundred thousand (1,500,000);
provided, however, that the number of shares constituting the Series B Preferred
Stock may be increased (but not above the total number of authorized shares of
preferred stock of the Corporation) or decreased (but not below the number of
shares of the Series B Preferred Stock then outstanding) by a certificate of
designations executed, acknowledged and filed with the Secretary of State of the
State of Delaware, in accordance with applicable law, setting forth a statement
that the specified increase or decrease therein has been authorized and directed
by a resolution or resolutions duly adopted by the Board of Directors.  No
further approval of any stockholder or stockholders of the Corporation
(including, without limitation, the holders of any shares of the Series B
Preferred Stock outstanding at such time) shall be required in connection
therewith.
<PAGE>

          3.   Dividends.  The holders of record of shares of the Series B
               ---------
Preferred Stock shall be entitled to receive dividends at a rate of 7.0% per
annum on the stated value of the Series B Preferred Stock ($100 per share),
payable in shares of Series B Preferred Stock or in cash out of funds legally
available therefor. The choice of the method of payment shall be at the option
of the Corporation. Dividends shall be payable annually on each anniversary of
the Original Issue Date or, if such date is not a Business Day, the next
succeeding Business Day. For purposes hereof, the term "Business Day" means a
day other than (i) a Saturday or Sunday or (ii) a day on which banking
institutions are authorized or required by law or executive order to remain
closed in the States of Texas or Virginia. Any unpaid dividends shall
accumulate. No dividends shall be paid on the common stock, par value $0.001 per
share, of the Corporation (the "Common Stock") or any other capital stock of the
Corporation until all accrued and unpaid dividends shall have been paid on the
Series B Preferred Stock and in the event the Board of Directors declares a
dividend to the holders of shares of Common Stock or other capital stock of the
Corporation, the Board of Directors shall at the same time declare a dividend
for the holders of the Series B Preferred Stock in an amount for each share of
Series B Preferred Stock equal to the dividend payable on the number of shares
of Common Stock into which shares of Series B Preferred Stock may be converted
or other capital stock of the Corporation.

          4.   Liquidation Preference. Upon any liquidation, dissolution or
               ----------------------
winding up of the Corporation, whether voluntary or involuntary (a
"Liquidation"), the holders of the shares of Series B Preferred Stock shall be
entitled, before any distribution or payment is made upon the Common Stock, to
be paid an amount equal to $100.00 per share plus all declared but unpaid
dividends to such date (collectively, the "Liquidation Preference"). After
setting apart for payment or paying in full the Liquidation Preference, the
remaining assets (whether stated capital or surplus), if any, and all
consideration received by the Corporation in excess of the Liquidation
Preference, shall be distributed to the holders of record of the issued and
outstanding shares of Common Stock. If upon any Liquidation of the Corporation,
whether voluntary or involuntary, the assets to be distributed among the holders
of Series B Preferred Stock shall be insufficient to permit payment in full of
the Liquidation Preference to the holders of Series B Preferred Stock, then the
entire assets of the Corporation shall be distributed ratably among such holders
in proportion to the full respective distributive amounts to which they are
entitled. Written notice of a Liquidation, stating a payment date, the estimated
amount of the Liquidation Preference, and the place where said amounts shall be
payable shall be given by mail not less than 20 days prior to the payment date
stated therein, to each holder of record of Series B Preferred Stock at his
address as shown by the records of the Corporation. Notwithstanding the
foregoing, however, the failure of the Corporation to give such notice, or any
defect therein, shall not affect the legality or validity of any dividend,
distribution or other action or event. Notwithstanding the provisions of Section
6(c) below, a transaction described in Section 6(c)(i) (excluding a transaction
within the exclusion set forth therein) or Section 6(c)(ii) shall, at the
election of one or more holders of the Series B Preferred Stock by written
notice to the Corporation within 10 days prior to the date that is before the
occurrence of such event, be deemed a Liquidation if the value of the cash,
property or securities per share received by the holders of the shares of Series
B Preferred Stock in such transaction would be less than the Liquidation
Preference. The foregoing election right of the holders of the Series B
Preferred Stock is exercisable by each of

                                       2
<PAGE>

such holders and the exercise by any holder thereof shall not affect the rights
of any other holders of Series B Preferred Stock.

          5.   Conversion.  The holders of the Series B Preferred Stock shall
               ----------
have the following conversion rights:

               (a)  Optional Conversion.  Each share of Series B Preferred Stock
                    -------------------
shall be convertible at any time, at the option of the holder of record thereof,
into fully paid and nonassessable shares of Common Stock at the "Conversion
Rate" (as defined in Section 5(c) below) then in effect upon surrender to the
Corporation or its transfer agent of the certificate or certificates
representing the shares of Series B Preferred Stock to be converted, as provided
below, or if the holder notifies the Corporation or its transfer agent that such
certificate or certificates have been lost, stolen or destroyed, upon the
execution and delivery of an agreement and security satisfactory to the
Corporation to indemnify the Corporation from any losses incurred by it in
connection therewith. Such conversion shall occur automatically upon receipt of
all applicable regulatory and other consents and approvals, and the Corporation
shall reasonably cooperate with the holders of the Series B Preferred Stock to
obtain all necessary consents and approvals.

               (b)  Mandatory Conversion. Beginning on the date which is 2 years
                    --------------------
from the date of the initial issuance of the Series B Preferred Stock (the
"Original Issue Date") until the date which is 5 years after the Original Issue
Date, the Corporation may require, by written notice to one or more of the
holders of the Series B Preferred Stock given at least 30 days prior to the date
of conversion, that all, but not less than all, of such holder's Series B
Preferred Stock shall be automatically converted into fully paid and
nonassessable shares of Common Stock at the Conversion Rate then in effect. Such
conversion shall occur automatically upon receipt of all applicable regulatory
and other consents and approvals, and the holders of the Series B Preferred
Stock shall reasonably cooperate with the Corporation to obtain all necessary
consents and approvals. In such event, the outstanding shares of Series B
Preferred Stock shall be converted automatically without any further action by
the holders of such shares and whether or not the certificates representing such
shares are surrendered to the Corporation or its transfer agent; provided,
                                                                 --------
however, that the Corporation shall have no right to require conversion of the
-------
Series B Preferred Stock if the average of the Closing Prices of the Common
Stock for the 30 trading days preceding the proposed date of conversion shall be
less than the Conversion Price and provided, further, that the Corporation shall
                                   --------  -------
not be obligated to issue certificates evidencing the shares of Common Stock
issuable upon such conversion unless certificates evidencing such shares of the
Series B Preferred Stock being converted are delivered to the Corporation or its
transfer agent, as provided below, or the holder notifies the Corporation or its
transfer agent that such certificates have been lost, stolen or destroyed and
executes and delivers an agreement and security satisfactory to the Corporation
to indemnify the Corporation from any losses incurred by it in connection
therewith. For purposes of this provision the "Closing Price" means, for any
security as of any date, the closing sale price for such security on the Nasdaq
Stock Market as reported by the consolidated transaction reporting system, or,
if the Nasdaq Stock Market is not the principal trading market for such
security, the last closing bid price of such security on the principal
securities exchange or trading market where such security is listed or traded as
reported by the consolidated transaction reporting system, or if the foregoing
do not apply, the last closing

                                       3
<PAGE>

bid price of such security in the over-the-counter market on the electronic
bulletin board for such security as reported by Bloomberg Financial Markets
("Bloomberg"), or, if no closing bid price is reported for such security by
Bloomberg, the last closing trade price of such security that is listed by
Bloomberg, or, if no last closing trade price is reported for such security by
Bloomberg, the average of the bid prices of any market makers for such security
as reported in the "pink sheets" by the National Quotation Bureau, Inc.

               (c)  Basis For Conversion; Converted Shares.  The basis for any
                    --------------------------------------
conversion under this Section 5 shall be the "Conversion Rate" in effect at the
time of conversion, which for the purposes hereof shall mean the number of
shares of Common Stock issuable with respect to each share of Series B Preferred
Stock to be converted under this Section 5. Initially, the Conversion Rate shall
be 3.2258:1 (i.e., 3.2258 shares of Common Stock for each share of Series B
Preferred Stock being converted). Such Conversion Rate shall be subject to
adjustment as provided in Section 6 below. As used herein, the term "Conversion
Price" initially shall be $31.00 per share of Common Stock, but shall be subject
to adjustment as provided herein. If any fractional interest in a share of
Common Stock would be deliverable upon conversion of Series B Preferred Stock,
the Corporation shall pay in lieu of such fractional share an amount equal to
the Conversion Price of such fractional share (computed to the nearest ten
thousandth of a share) in effect at the close of business on the date of
conversion. Any shares of Series B Preferred Stock which have been converted
shall be canceled and the certificates representing shares of Series B Preferred
Stock so converted shall represent the right to receive (x) such number of
shares of Common Stock into which such shares of Series B Preferred Stock are
convertible, plus (y) cash payable for any fractional share plus (z) all accrued
but unpaid dividends relating to such shares. Upon the conversion of shares of
Series B Preferred Stock as provided in this Section 5, the Corporation shall
promptly pay all then declared and accrued but unpaid dividends to the holder of
the Series B Preferred Stock being converted, if any. The Board of Directors
shall at all times reserve a sufficient number of authorized but unissued shares
of Common Stock to be issued in satisfaction of the conversion rights and
privileges aforesaid.

               (d)  Mechanics of Conversion.  Before any holder of shares of
                    -----------------------
Series B Preferred Stock shall be entitled to convert the same into shares of
Common Stock, such holder shall surrender the certificate or certificates
therefor, duly endorsed, or deliver an appropriate indemnity agreement and
security, at the office of the Corporation or its transfer agent for the Series
B Preferred Stock and in the case of a conversion pursuant to Section 5(a)
above, shall give written notice to the Corporation of the election to convert
the same and shall state therein the name or names in which the certificate or
certificates for shares of Common Stock are to be issued. The Corporation shall,
as soon as practicable thereafter, issue and deliver at such office to such
holder of Series B Preferred Stock, or to the nominee or nominees of such
holder, a certificate or certificates for the number of shares of Common Stock
to which such holder shall be entitled as aforesaid. A certificate or
certificates will be issued for the remaining shares of Series B Preferred Stock
in any case in which fewer than all of the shares of Series B Preferred Stock
represented by a certificate are converted.

          6.   Adjustment of Conversion Price and Conversion Rate.  The number
               --------------------------------------------------
and kind of securities issuable upon the conversion of the Series B Preferred
Stock, the Conversion

                                       4
<PAGE>

Price and the Conversion Rate shall be subject to adjustment from time to time
in accordance with the following provisions:

               (a)  Definition of Common Stock.  For purposes of this Section 6,
                    --------------------------
the term "Common Stock" shall be deemed to mean the Common Stock and the stock
of the Corporation of any class, or series within a class, whether now or
hereafter authorized, which has the right to participate in the distribution of
either earnings or assets of the Corporation without limit as to the amount.

               (b)  Reorganization; Share Exchange; Reclassification.  In the
                    ------------------------------------------------
event of a reorganization, share exchange, or reclassification, other than a
change in par value, or from par value to no par value, or from no par value to
par value or a transaction described in subsection (c) or (d) below, each share
of Series B Preferred Stock shall, after such reorganization, share exchange or
reclassification, be convertible into the kind and number of shares of stock or
other securities or other property of the Corporation which the holder of Series
B Preferred Stock would have been entitled to receive if the holder had held the
Common Stock issuable upon conversion of such share of Series B Preferred Stock
immediately prior to such reorganization, share exchange, or reclassification.

               (c)  Merger; Consolidation.  If (i) the Corporation consolidates
                    ---------------------
or merges into or with any other corporation or corporations or any other entity
or entities (excluding any merger or consolidation in which the Corporation is
the surviving corporation and, after giving effect thereto, the holders of the
Corporation's outstanding capital stock (on a fully-diluted, as-converted basis)
immediately prior to such merger or consolidation will own more than 50% of the
outstanding capital stock of the Corporation (on a fully-diluted, as-converted
basis) immediately following such merger or consolidation), or (ii) in a single
transaction or a series of related transactions, the Corporation sells or
transfers all or substantially all its assets, each share of Series B Preferred
Stock shall, after such merger, consolidation or transaction(s), be convertible
into the kind and number of shares of stock and/or other securities, cash or
other property which the holder of such share of Series B Preferred Stock would
have been entitled to receive if the holder had held the Common Stock issuable
upon conversion of such share of Series B Preferred Stock immediately prior to
such merger, consolidation or transaction(s).

               (d)  Subdivision or Combination of Shares.  In case outstanding
                    ------------------------------------
shares of Common Stock shall be subdivided, the Conversion Price shall be
proportionately reduced as of the effective date of such subdivision.  In case
outstanding shares of Common Stock shall be combined, the Conversion Price shall
be proportionately increased as of the effective date of such combination.

               (e)  Stock Dividends.  In case shares of Common Stock are issued
                    ---------------
as a dividend or other distribution on the Common Stock, then the Conversion
Price shall be adjusted, as of the earliest of the date of such declaration,
payment or other distribution, to that price determined by multiplying the
Conversion Price in effect immediately prior to such declaration, payment or
other distribution by a fraction (i) the numerator of which shall be the number
of shares of Common Stock outstanding immediately prior to the payment of such
dividend or other

                                       5
<PAGE>

distribution, and (ii) the denominator of which shall be the total number of
shares of Common Stock outstanding immediately after the payment of such
dividend or other distribution. In the event that the Corporation shall declare
or pay any dividend on the Common Stock payable in any right to acquire Common
Stock for no consideration, then the Corporation shall be deemed to have made a
dividend payable in Common Stock on an amount of shares equal to the maximum
number of shares issuable upon exercise of such rights to acquire Common Stock.

               (f)  Adjustment of Conversion Rate.  Upon each adjustment of the
                    -----------------------------
Conversion Price under the provisions of this Section 6, the Conversion Rate
shall be adjusted to an amount determined by dividing  $100 by such adjusted
Conversion Price.

               (g)  Other Provisions Applicable to Adjustment Under this
                    ----------------------------------------------------
Section.  The following provisions will be applicable to the adjustments in the
-------
Conversion Price and the Conversion Rate as provided in this Section 6:

                    (i)   Treasury Shares.  The number of shares of Common Stock
                          ---------------
at any time outstanding shall not include any shares thereof then directly or
indirectly owned or held by or for the account of the Corporation. For purposes
of this Section 6, the sale or other disposition of any Common Stock of the
Corporation theretofore held in its treasury shall, unless otherwise set forth
herein, be deemed to be an issuance thereof.

                    (ii)  Other Action Affecting Common Stock.  In case the
                          -----------------------------------
Corporation shall take any action affecting the outstanding number of shares of
Common Stock other than an action described in any of the foregoing subsections
6(b) to 6(e) hereof, inclusive, which would have an inequitable or dilutive
effect on the relative percentage ownership interests of the holders of Series B
Preferred Stock that could not have been cured or avoided by the holders of the
Series B Preferred Stock by their exercise of any available rights of first
offer, the Conversion Price shall be adjusted in such manner and at such time as
the Board of Directors of the Corporation on the advice of the Corporation's
independent public accountants may in good faith determine to be equitable in
the circumstances.

                    (iii) Minimum Adjustment.  No adjustment of the Conversion
                          ------------------
Price shall be made if the amount of any such adjustment would be an amount less
than 1% of the then applicable Conversion Price, but any such amount shall be
carried forward and an adjustment with respect thereof shall be made at the time
of and together with any subsequent adjustment which, together with such amount
and any other amount or amounts so carried forward, shall aggregate an increase
or decrease of 1% or more of the then applicable Conversion Price.

               (h)  Notices of Adjustments.  Whenever the Conversion Rate and
                    ----------------------
Conversion Price is adjusted as herein provided, an officer of the Corporation
shall compute the adjusted Conversion Rate and Conversion Price in accordance
with the foregoing provisions and shall prepare a written certificate setting
forth such adjusted Conversion Rate and Conversion Price and showing in detail
the facts upon which such adjustment is based, and such written instrument shall
promptly be delivered to the record holders of the Series B Preferred Stock.

                                       6
<PAGE>

          7.   Notices of Record Dates and Effective Dates.  In case (i) the
               -------------------------------------------
Corporation shall declare a dividend (or any other distribution) on the Common
Stock payable otherwise than in shares of Common Stock; (ii) the Corporation
shall authorize the granting to the holders of Common Stock of rights to
subscribe for or purchase any shares of capital stock of any class or any other
rights; (iii) of any reorganization, share exchange or reclassification of the
capital stock of the Corporation, or of any consolidation or merger to which the
Corporation is party or of the sale, lease or exchange of all or substantially
all of the property of the Corporation; or, (iv) of a Liquidation, then the
Corporation shall cause to be mailed to the record holders of the Series B
Preferred Stock at least 20 days prior to the applicable record date or
effective date hereinafter specified, a notice stating the date on which a
record is to be taken for the purpose of such dividend, distribution or rights,
or, if a record is not to be taken, the date as of which the holders of record
of Common Stock to be entitled to such dividend, distribution or rights are to
be determined or  the date on which such dividend, granting of rights,
reclassification, reorganization, share exchange, consolidation, merger, sale,
lease, exchange, or Liquidation is expected to become effective, and the date as
of which it is expected that holders of record of Common Stock shall be entitled
to exchange their shares of Common Stock for securities or other property
deliverable upon such dividend, granting of rights, reclassification,
reorganization share exchange, consolidation, liquidation, merger, sale, lease,
exchange, dissolution or Liquidation.

          8.   Voting Rights.  Holders of Series B Preferred Stock shall be
               -------------
entitled to notice of any stockholder's meeting. However, the holders of shares
of Series B Preferred Stock shall not be entitled to vote upon any matters upon
which holders of the Common Stock have the right to vote. Upon conversion of
Series B Preferred Stock to Common Stock, the holders of such Common Stock shall
be entitled to such voting rights with respect to such Common Stock as the other
holders of Common Stock.

          9.   Redemption.  Except as provided below, at any time after 2 years
               ----------
from the Original Issue Date, any holder of Series B Preferred Stock shall have
the right to require the Corporation to redeem all or any shares of Series B
Preferred Stock then held by such holder (the "Redemption Right") at a price
equal to the original purchase price paid to the Corporation by such holder,
plus any accrued but unpaid dividends (the "Series B Redemption Price"). In the
event that the average of the Closing Prices of the Common Stock of NAS for the
30 trading days preceding the second, third, fourth, fifth or sixth
anniversaries of the Original Issue Date shall be less than the Conversion Price
(a "Low Stock Price Condition"), then the Corporation may, by written notice
(the "Extension Notice"), elect to postpone the holder's Redemption Right until
the next following anniversary of the Original Issue Date. The Extension Notice
shall be effective only if delivered on the first Business Day following the
pertinent anniversary date of the Original Issue Date or, if such anniversary
date is not a Business Day, then the date for delivery of the Extension Notice
shall be the next Business Day. The Company's right to postpone the holder's
Redemption Right for such one-year periods shall not be available for the one-
year period following any anniversary date in which the Company was entitled to
deliver an Extension Notice and failed to do so on a timely basis. The Company's
right to postpone the holder's Redemption Right for such one-year periods shall
expire on the sixth anniversary of the Original Issue Date. The holders shall in
any event have the right to require redemption from and after the seventh
anniversary of the Original Issue Date. Payment of the Series B

                                       7
<PAGE>

Redemption Price to the holders of Series B Preferred Stock shall be made by the
Corporation from any source of funds legally available therefor within 90
business days  (the "Series B Redemption Date"). Any holder of shares of the
Series B Preferred Stock wishing to exercise such redemption right shall give
written notice (the "Series B Redemption Notice") by mail, postage prepaid, to
the Corporation of such holders' intention to exercise such redemption right.
Such notice shall state the intention of such holder to exercise its redemption
rights and shall set forth the number of shares of Series B Preferred Stock in
respect of which redemption is demanded. Prior to payment of the Series B
Redemption Price, each holder of shares of Series B Preferred Stock who shall
have requested that such holder's shares of Series B Preferred Stock be so
redeemed shall surrender the certificate or certificates evidencing such shares
to the Corporation.  In the case of any certificate or certificates which have
been lost, stolen or destroyed, the holder of such certificate or certificates
shall make, execute and deliver an agreement and security satisfactory to the
Corporation to indemnify the Corporation from any losses incurred by it in
connection therewith.

          10.  Amendment; Waiver.  Except as expressly prohibited by Delaware
               -----------------
law, this Certificate of Designation may be amended and any provision herein may
be waived with the approval of the holders of a majority of the Series B
Preferred Stock and the Board of Directors.  Any amendment or waiver so effected
shall be binding upon each holder of Series B Preferred Stock.

[Signature Page Follows]

                                       8
<PAGE>

          IN WITNESS WHEREOF, this Certificate has been signed by the President
and Chief Executive Officer and attested to by the Secretary of Network Access
Solutions Corporation this ____ day of __________, 2000.


                                             By:____________________________

By:_________________________
   Secretary

                                       9