AGREEMENT AND PLAN OF MERGER

                                                                     Exhibit 2.1

                                 AMENDMENT NO. 1
                                       TO
                          AGREEMENT AND PLAN OF MERGER

                  THIS AMENDMENT NO. 1 TO AGREEMENT AND PLAN OF MERGER (this
"Amendment") is made and entered into as of this 22nd day of December, 2006, by
and among US LEC Corp, a Delaware corporation ("US LEC"), PAETEC Corp., a
Delaware corporation ("PAETEC"), WC Acquisition Holdings Corp., a Delaware
corporation and a wholly-owned direct subsidiary of PAETEC (the "Company"), WC
Acquisition Sub U Corp., a Delaware corporation and a wholly-owned direct
subsidiary of the Company ("Merger Sub U"), and WC Acquisition Sub P Corp., a
Delaware corporation and a wholly-owned direct subsidiary of the Company
("Merger Sub P").

                              W I T N E S S E T H:
                              - - - - - - - - - -

                  WHEREAS, the parties wish to amend the Agreement and Plan of
Merger, dated as of August 11, 2006, by and among US LEC, PAETEC, Merger Sub U,
Merger Sub P and the Company (the "Merger Agreement") upon the terms and
conditions set forth in this Amendment;

                  NOW, THEREFORE, in consideration of the foregoing and for
other good and valuable consideration, the receipt and sufficiency of which is
hereby acknowledged, the parties hereto hereby agree as follows:

         1. Amendment of Section 1.6(a). Section 1.6(a) of the Merger Agreement
is hereby amended by replacing the existing text with the following text:

                  "The directors of US LEC at the US LEC Effective Time shall be
                  the initial directors of the US LEC Surviving Corporation
                  until they have resigned or been removed from office or their
                  successors have been duly elected or appointed or qualified;
                  provided, however, that, within one day following the US LEC
                  Effective Time, the Company, as the sole stockholder of the US
                  LEC Surviving Corporation, shall take action to remove from
                  office without cause all such directors who are not also
                  continuing as directors of the Company."

          2. Amendment of Section 1.7(c). Section 1.7(c) of the Merger Agreement
is hereby amended by replacing the reference to "PAETEC Communications Corp."
set forth therein with a reference to "PAETEC Holding Corp."

         3. Amendment to Exhibits 1.7(a)-1 and 1.7(a)-2. Exhibits 1.7(a)-1 and
1.7(a)-2 to the Merger Agreement shall each be amended by replacing each
reference to "PAETEC Communications Corp." set forth therein with a reference to
"PAETEC Holding Corp."

         4. Amendment of Section 2.1. Section 2.1 of the Merger Agreement is
hereby amended by adding a new Section 2.1(j) thereto, which shall read in its
entirety as follows:

                           "(j) Cancellation of Company Shares. Each share of
                  CompanyCommon Stock held by PAETEC immediately prior to the
                  Effective Time shall automatically be canceled and retired and
                  shall cease to exist, and no consideration shall be delivered
                  in exchange therefor."

         5. Amendments Regarding Conversion Agreement.

                  (a) Section 5.17 of the Merger Agreement is hereby amended by
adding the following parenthetical at the end of such Section 5.17:

                  "(other than any amendment to or modification or termination
                  of the Conversion Agreement that provides for the acceleration
                  of the issuance and delivery of the shares of PAETEC Common
                  Stock subject to issuance p