<PAGE>   1
    First Amendment to Loan Agreement and Promissory Note     Exhibit No: 10.6.2


        This First Amendment to the Loan Agreement and Promissory Note is dated
April 24, 2001 and entered into by and between Clayton A. Thomas, Jr.
("Borrower") and Net2000 Communications Group, Inc. ("Company").

        WHEREAS, Borrower and Company entered into a letter agreement ("Loan
Agreement") dated December 5, 2000 in which the Company agreed to lend Borrower
an aggregate principal amount of up to $1,500,000 (collectively, the "Loan");
and

        WHEREAS, under the current terms of the Agreement, the loan matures and
is payable in full to the Company on June 5, 2001 ("Maturity Date");

        WHEREAS, the obligation of the Borrower to repay the Loan was evidenced
by a Promissory Note ("Note") dated December 5, 2000 and signed by Borrower;

        WHEREAS, under the current terms of the Note, the Borrower is obligated
to pay to the Company on each Payment Date (as defined in the Note) interest on
the outstanding principal balance of the Loan at the Prime Rate (as defined in
the Note) plus a margin of 1% per annum ("Interest Rate");

        WHEREAS, the parties wish to amend the Maturity Date in the Loan
Agreement and the Interest Rate in the Note;

        NOW, THEREFORE, the parties agree as follows:

1.      The second sentence of Paragraph 1 of the Loan Agreement is deleted in
its entirety and replaced with the following sentence:

        "The Loan matures, and shall be due and payable (together with all
        accrued interest thereon) on June 30, 2002 ("Maturity Date").


2.      Paragraph 2 of the Note is deleted in its entirety and replaced with the
following new Paragraph 2:

        "Interest Rate Provisions. Except as provided in Section 2.2 hereof,
        from the date hereof and thereafter until the outstanding amount hereof
        is paid in full, interest shall accrue on the principal balance of this
        Note outstanding from time to time at the Applicable Federal Rate
        ("AFR") in effect at the end of each month as published by the United
        States Internal Revenue Service ("Interest Rate"), and shall be paid
        currently in cash on a monthly basis on each Payment Date (as defined
        below). Each change in any interest rate provided for herein based upon
        the AFR resulting from a change in the AFR shall take effect without
        notice to the Borrower at the time of such change in the AFR."


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3.      All other terms, conditions, and obligations of the Loan Agreement and
Promissory Note shall remain in full force and effect unless amended in writing
and signed by both parties.

        IN WITNESS WHEREOF, the parties hereto have caused this First Amendment
to the Loan Agreement and Promissory Note be duly executed and effective as of
February 1, 2001.



NET2000 COMMUNICATIONS GROUP, INC.               /s/ Clayton A. Thomas, Jr.
                                               ----------------------------
                                               CLAYTON A. THOMAS, JR.,
                                                 AS BORROWER


BY:   /s/ Donald Clarke
     ---------------------
      Donald Clarke
      Chief Financial Officer


COMMONWEALTH OF VIRGINIA )
                         ) ss:
COUNTY OF FAIRFAX        )

        On this 4th day of May, 2001 before me personally appeared CLAYTON A.
THOMAS, JR., to be known to be the person who executed the foregoing instrument
and who being by me duly sworn, did depose and say that he signed his name to
the foregoing instrument.

                                                /s/ Cathy Riehn
                                              -------------------
                                              NOTARY PUBLIC


My commission expires on:  11/30/2004