<PAGE>
                                                                EXHIBIT 10.28(g)

                               AMENDMENT NO. 1 TO
                   MINI-MED/DENTAL BENEFIT EXTENSION AGREEMENT

         THIS AMENDMENT NO. 1 TO MINI-MED/DENTAL BENEFIT EXTENSION AGREEMENT
(the "Amendment") is made and entered into this 14th day of August, 2001, by and
between Atmos Energy Corporation, a Texas and Virginia corporation (the
"Company"), and CHARLES K. VAUGHAN ("Mr. Vaughan").

         WHEREAS, the Company and Mr. Vaughan entered into that certain
Mini-Med/Dental Benefit Extension Agreement dated October 1, 1994, (the
"Agreement"); and

         WHEREAS, the Company and Consultant desire to amend the Agreement as
set forth below to provide for an extension of the benefits under the Agreement
to Mr. Vaughan and his eligible dependents for his and his surviving spouse's
lifetimes.

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

         1. Benefits Provided to Mr. Vaughan's Surviving Spouse. Section 2 of
the Agreement shall be amended and restated in its entirety to read as follows:

                  If Mr. Vaughan dies prior to reaching age 65 and leaves a
                  surviving spouse, said spouse shall, for the remainder of her
                  life, be entitled to the benefits being provided to Mr.
                  Vaughan under Section 1 hereof, as if Mr. Vaughan had not
                  died.

         2. Term of the Agreement. Section 3 of the Agreement shall be amended
and restated in its entirety to read as follows:

                  The term of this Agreement shall commence on the Effective
                  Date and shall end on the date Mr. Vaughan dies.
                  Notwithstanding the foregoing provision of this Section 3, as
                  provided in Section 2, in the event Mr. Vaughan leaves a
                  surviving spouse at the time of his death, the term of this
                  Agreement shall not end until the date such surviving spouse
                  dies.

         3. No Other Amendment. Except as expressly amended hereby, all of the
other terms, provisions, and conditions of the Agreement are hereby ratified and
confirmed and shall remain unchanged and in full force and effect. To the extent
any terms or provisions of this Amendment conflict with those of the Agreement,
the terms and provisions of the Agreement shall control. This Amendment shall be
deemed a part of, and is hereby incorporated into the Agreement. The Agreement
and any and all other documents heretofore, now, or hereafter executed and
delivered pursuant to the terms of the Agreement are hereby amended so that any
reference to the Agreement shall mean a reference to the Agreement as amended
hereby.


<PAGE>

         4. Governing Law. This Amendment shall be governed by, and construed in
accordance with, the laws of the State of Texas.

         5. Counterparts. This Amendment may be executed in counterparts, each
of which will be an original, but all of which together will constitute one and
the same agreement.

         IN WITNESS WHEREOF, the parties hereto have executed this Amendment
effective as of the date and year first above written.

                                                COMPANY

                                                ATMOS ENERGY CORPORATION


                                                By: /s/ ROBERT W. BEST
                                                    ---------------------------
                                                    Robert W. Best
                                                    Chairman, President and
                                                    Chief Executive Officer


                                                    /s/ CHARLES K. VAUGHAN
                                                    ---------------------------
                                                    CHARLES K. VAUGHAN