<PAGE>

                                       EXHIBIT 10.4. 7

                                 AMENDMENT NO. 6

                                       TO

                                 SUPPLY AGREEMENT

                                     BETWEEN

                         DOBSON COMMUNICATIONS CORPORATION

                                       AND

                               NORTEL NETWORKS INC.,

                           (f/k/a NORTHERN TELECOM INC.)

This amendment is made effective as of the date last signed ("Effective Date
No. 6") by and between Dobson Communications Corporation, an Oklahoma
corporation, with offices at 13439 North Broadway Extension, Suite 200,
Oklahoma City, Oklahoma  73114 (hereinafter referred to as "Buyer") and
Nortel Networks Inc., (f/k/a "Northern Telecom Inc.") a Delaware corporation
with offices at 2350 Lakeside Blvd., Richardson, Texas  75082 (hereinafter
referred to as "Seller").

WHEREAS, Buyer and Seller entered into a Supply Agreement as of December 6,
1995, as amended ("Agreement"); and,

WHEREAS, Buyer and Seller now wish to further amend the Agreement to include,
among other things, an increase in Buyer's purchase commitment, increased
discounts from Seller, assurance of Seller's presence in future
Seller-equipped markets and provide Seller with a last-bid opportunity, all
as further described herein;

NOW, THEREFORE, in consideration of the mutual covenants herein contained,
Buyer and Seller agree to amend the Agreement as follows:

    1.  Replace all references to "Northern Telecom Inc." in the Agreement,
        and its amendments, with "Nortel Networks Inc."

    2.  Increase the Buyer's purchase commitment by amending the last
        sentence of Article 4 ("Price") (as amended in Section 3 of Amendment
        No. 5), changing the dollar amount of "$120 million" to "two hundred
        fifteen million dollars ($215,000,000), of which approximately
        $78,000,000 has been purchased against the cumulative commitment prior
        to this Amendment No. 6."

    3.  Amend Annex 1A "Extended Term Equipment and Services Pricing"
        (Schedule A to Amendment No. 2, as last amended in Amendment No. 5), as
        follows:

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        (a)  by deleting the amount "$5.00" and replacing it with "$4.00" in
             Section 4.1

        (b)  by deleting the amount "$3,990" and replacing it with "$3,325",
             and adding the words "for either 800 MHz or 1900 MHz radios.", at
             the end of the sentence.

    4.  Amend the subsections of Section 5.2 of Annex 1A, as follows:

        (a)  Add the following language to the beginning of Subsection 5.2.1:
             "Subject to changes to Subsection 5.2.1(a), below,"

        (b)  Change the level of "Discount off Seller's then-current List
             Price" of the following items in Subsection 5.2.1(a), as indicated
             below, effective as of the effective date of this Amendment No. 6:

<TABLE>
<CAPTION>
             Description           Discount off Seller's then-current List Price
             -----------           ---------------------------------------------
<S>                                <C>
             Switch/TDMA Hardware                       65%
             Cell Site Hardware
             (exclusive of
             radios/amplifiers)                         65%
             (Note:  This discount level applies to either 800 MHz or 1900MHz Equipment.)
</TABLE>

    5.  Add new Section 8.0 to Annex 1A, as follows:

        "8.0 NORTEL NETWORKS EQUIPMENT IN NEWLY ACQUIRED MARKETS

        In the event Buyer acquires markets in the future that contain
        current MTX-Software based Seller's equipment, Buyer agrees that if it
        replaces such equipment, it will do so with Nortel Networks' Equipment,
        only"

    6.  Add new Section 9.0 to Annex 1A, as follows:

        "9.0 LAST BID OPPORTUNITY

        Subject to Section 9.1 below, and in the event Section 8.0 is not
        applicable, in each and every case in which Buyer request Seller and
        one or more other wireless infrastructure equipment vendors to provide
        a bid or offer to sell with respect to Buyer's purchase of wireless
        equipment, Buyer shall give Seller an opportunity to provide a last bid
        or offer to sell such equipment after all other vendors have made their
        bid(s) or offer(s) ("Last Bid").  Such Last Bid may be Seller's first
        opportunity to bid or offer, or may be a bid or offer by Seller
        subsequent to its first bid or offer.

        At such time as no further bids or offers are being accepted by Buyer
        from vendors other than Seller, Buyer shall notify Seller in writing,
        with written receipt from Seller, that Seller may make its Last Bid.
        Within twenty-four (24) hours after Seller's receipt of Last Bid notice
        from Buyer, Seller shall either provide its Last Bid or provide Buyer
        with written notice declining to make a Last Bid.

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        Should Seller fail to respond to Buyer within twenty-four (24) hours
        after notice of Last Bid, Buyer may deem that Seller has declined to
        offer such Last Bid.

        9.1  Buyer shall not be required to solicit any bid or offer from
        Seller for the sale of wireless infrastructure equipment, nor shall
        Buyer be required to accept a Last Bid as the winning bid or offer."

    7.  Amend Article I, Section 1.21 "Extended Term", (as amended by Amendment
        No. 5), by deleting the words "ending December 31, 2002", and replacing
        them with "ending three (3) years from the effective date of this
        Amendment No. 6."

    8.  Amend Article 2, Scope, by adding the following Section 2.2:

        "2.2  Buyer and Seller acknowledge and agree that Buyer's purchase
              commitment may be fulfilled by purchases for the use of either
              (i) Buyer, and its majority owned subsidiaries, as such are made
              known to Seller in writing, with Buyer irrevocably accepting
              responsibility for the performance of such subsidiaries, or
              (ii) American Cellular Corporation ("ACC") and its majority owned
              subsidiaries, as such are made known to Seller in writing, with
              Buyer irrevocably accepting responsibility for the performance of
              such subsidiaries, so long as Buyer or one of its majority owned
              subsidiaries is the manager of ACC.  In the event that Buyer, or
              one of its such majority owned subsidiaries no longer is the
              manager of ACC, and there remains an unfulfilled purchase
              commitment under the Agreement, Buyer and Seller agree to assign
              and allocate up to thirty three percent (33%) of the unfulfilled
              commitment to ACC upon a new agreement between Seller and ACC
              being entered into with substantially similar terms as then in
              effect between Buyer and Seller, and upon ACC's written
              acceptance of such assignment, to reduce Buyer's remaining
              commitment by such assigned amount.  A current listing of Buyer's
              majority owned subsidiaries is provided at Attachment B, which
              may be amended, as necessary, upon receipt of written
              notification by Buyer."

    9.  Amend Article 2, Scope, by adding the following Section 2.3:

        "2.3A  Purchase Order submitted by a subsidiary of Buyer, as listed
               in Schedule B to this Amendment No. 6, pursuant to the terms and
               conditions of this Agreement, and which Seller has accepted,
               constitutes a Contract between the subsidiary ordering and
               Seller.  As used herein, "Contract" shall mean an agreement for
               the supply of Equipment and/or Services between (i) any such
               subsidiary of Buyer and (ii) Seller, which comes into effect by
               the acceptance of a Purchase Order pursuant to the provisions of
               this Agreement, and which Contract shall be governed solely by
               the terms and conditions of this Agreement; and each reference
               to "Buyer" in this Agreement shall for such Contract mean the
               ordering subsidiary.  Buyer absolutely, irrevocably and
               unconditionally guarantees the performance of every Buyer
               subsidiary issuing Purchase Orders and/or otherwise acting

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               under this Agreement and any Contract created thereby.  Buyer
               hereby expressly waives any other diligence, protest or notice
               as well as any requirement that Seller exhaust any remedy or
               right against such Buyer subsidiary."

    10. Amend Annex 1A, "Extended Term Equipment and Services Pricing" of
        Schedule A to Amendment No. 2, by adding the "Combined 1900 MHz and
        800 MHz Pricing for OK-4 and OK-6 Markets" as Schedule A to this
        Amendment No. 6.

    11. Amend Schedule A to Amendment No. 5, Section 7.3, "Co-operative
        Marketing Funds" as follows:

        Delete Section 7.3 in its entirety and replace it with:

        "7.3  CO-OPERATIVE MARKING FUNDS

        7.3.1 For the purposes of this Section 7.3 only, beginning on
              Effective Date No. 6, during each period as shown below, and
              in consideration of the provision of co-operative marketing
              funds by Seller ("Co-op Funds"), as hereinafter described,
              Buyer agrees to submit Purchase Orders to Seller for Equipment
              for a minimum of $40 million dollars in net Prices as set forth
              in Amendment No. 5 for each calendar year, beginning on
              Effective Date No. 6.  Seller will submit Co-op Fund payments
              based on the following schedule:

<TABLE>
<S>                                                   <C>
              Period 1:                               Co-Op Funds Available
                                                      ---------------------
                Payment #1:  (January 15, 2001)               $1.5M
                Payment #2:  (April 15, 2001)                 $1.5M
              Period 2:
                Payment #3:  (January 15, 2002)               $1.5M
                Payment #4:  (April 15, 2002)                 $1.5M
              Period 3:
                Payment #5:  (January 15, 2003)               $1.5M
                Payment #6:  (April 15, 2003)                 $1.5M
</TABLE>

        7.3.2 In the event Buyer does not fulfill each of its $40M per
              calendar year commitments with Seller, as calculated from
              Effective Date No. 6, Buyer will refund the amount of Co-op
              Funds relative to the percentage of commitment not met, upon
              Seller's request.  Buyer shall take delivery of all Equipment
              purchased in any period within twelve (12) months of Seller's
              receipt of Buyer's Purchase Order therefore.

        7.3.3 The total amount of Co-op Funds that Seller shall be obligated
              to provide under this Agreement shall not exceed a total of three
              million dollars ($3,000,000) for any designated period.  Buyer
              shall use all Co-op Funds

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              solely for Buyer's marketing and/or advertising wherein Seller's
              Equipment is featured and/or referenced.

        7.3.4 As a condition to Seller providing Buyer with applicable Co-op
              Funds, as set forth above, Buyer shall provide Seller with the
              following: (i) payment in full for any invoices issued by Seller
              for Purchase Orders received and accepted during the applicable
              period which have become due; (ii) a written, detailed
              description of Buyer's marketing and/or advertising plan for the
              period immediately following the period used to calculate such
              applicable Co-operative Marketing Funds; and (iii) a written
              request for payment of such previously earned Co-operative
              Marketing Funds."

    12. Upon receipt by Seller of Buyer's irrevocable Purchase Order(s) for
        the Equipment comprising the OK-4 and OK-6 1900 MHz and 800 MHz
        Equipment, as provided at Schedule A to this Amendment No. 6, and upon
        Seller receiving Buyer's proposal for the use of additional Co-op
        Funds, Seller will pay Buyer an additional two million dollars ($2
        million) in Co-op Funds over and above those provided for in Article 11
        above, of this Amendment No. 6.  Buyer will be required to notify Seller
        three (3) weeks in advance of the desired payment date.

    13. Except as specifically modified by Amendment Nos. 1 through 5, and
        this Amendment No. 6, the Agreement in all other respects shall
        continue in full force and effect.

IN WITNESS WHEREOF, the parties have caused this Amendment No. 6 to be signed
by their duly authorized representatives and effective as of the date first
set forth above.

DOBSON COMMUNICATIONS               NORTEL NETWORKS INC.
CORPORATION
By:                                 By:
   ------------------------------      -----------------------------------------

Name:  G. Edward Evans              Name:  Tonya L. Lowe

Title:  President & COO             Title:  Vice President, Marketing Operations

Date:  6-30-00                      Date:  3/30/00