<PAGE>
                                                               EXHIBIT (4)(i)(d)

                             SUPPLEMENTAL INDENTURE

     Supplemental Indenture (this "Supplemental Indenture"), dated as of March
11, 2002, among Georgia PCS Management, LLC and Georgia PCS Leasing, LLC, both
Georgia limited liability companies (collectively the "Guaranteeing
Subsidiary"), and subsidiaries of US Unwired Inc., a Louisiana corporation (the
"Company"), the Company, the other Guarantors (as defined in the Indenture
referred to herein) and State Street Bank and Trust Company, as trustee under
the indenture referred to below (the "Trustee").

                                   WITNESSETH

     WHEREAS, the Company has heretofore executed and delivered to the Trustee
an indenture (the "Indenture"), dated as of October 29, 1999 providing for the
issuance of an aggregate principal amount at maturity of up to $400 million of
13 3/8% Senior Subordinated Discount Notes due 2009 (the "Notes");

     WHEREAS, the Indenture provides that under certain circumstances the
Guaranteeing Subsidiary shall execute and deliver to the Trustee a supplemental
indenture pursuant to which the Guaranteeing Subsidiary shall unconditionally
guarantee all of the Company's Obligations under the Notes and the Indenture on
the terms and conditions set forth herein (the "Note Guarantee"); and

     WHEREAS, pursuant to Section 9.01 of the Indenture, the Trustee is
authorized to execute and deliver this Supplemental Indenture.

     NOW THEREFORE, in consideration of the foregoing and for other good and
valuable consideration, the receipt of which is hereby acknowledged, the
Guaranteeing Subsidiary and the Trustee mutually covenant and agree for the
equal and ratable benefit of the Holders of the Notes as follows:

     1. Capitalized Terms. Capitalized terms used herein without definition
shall have the meanings assigned to them in the Indenture.

     2. Agreement to Guarantee. The Guaranteeing Subsidiary hereby agrees as
follows:

          (a) Along with all Guarantors named in the Indenture, to jointly and
     severally Guarantee to each Holder of a Note authenticated and delivered by
     the Trustee and to the Trustee and its successors and assigns, the Notes or
     the obligations of the Company hereunder or thereunder, that:

               (i) the principal and interest on the Notes will be promptly paid
          in full when due, whether at maturity, by acceleration, redemption or
          otherwise, and interest on the overdue principal of and interest on
          the Notes, if any, if lawful, and all other obligations of the Company
          to the Holders or the Trustee hereunder or thereunder will be promptly
          paid in full or performed, all in accordance with the terms hereof and
          thereof; and

<PAGE>

               (ii) in case of any extension of time of payment or renewal of
          any Notes or any of such other obligations, that same will be promptly
          paid in full when due or performed in accordance with the terms of the
          extension or renewal, whether at stated maturity, by acceleration or
          otherwise. Failing payment when due of any amount so guaranteed or any
          performance so guaranteed for whatever reason, the Guarantors shall be
          jointly and severally obligated to pay the same immediately.

          (b) The obligations hereunder shall be unconditional, irrespective of
     the validity, regularity or enforceability of the Notes or the Indenture,
     the absence of any action to enforce the same, any waiver or consent by any
     Holder of the Notes with respect to any provisions hereof or thereof, the
     recovery of any judgment against the Company, any action to enforce the
     same or any other circumstance which might otherwise constitute a legal or
     equitable discharge or defense of a guarantor.

          (c) The following is hereby waived: diligence, presentment, demand of
     payment, filing of claims with a court in the event of insolvency or
     bankruptcy of the Company, any right to require a proceeding first against
     the Company, protest, notice and all demands whatsoever.

          (d) This Note Guarantee shall not be discharged except by complete
     performance of the obligations contained in the Notes and the Indenture,
     and the Guaranteeing Subsidiary accepts all obligations of a Guarantor
     under the Indenture.

          (e) If any Holder or the Trustee is required by any court or otherwise
     to return to the Company, the Guarantors, or any Custodian, Trustee,
     liquidator or other similar official acting in relation to either the
     Company or the Guarantors, any amount paid by either to the Trustee or such
     Holder, this Note Guarantee, to the extent theretofore discharged, shall be
     reinstated in full force and effect.

          (f) The Guaranteeing Subsidiary shall not be entitled to any right of
     subrogation in relation to the Holders in respect of any obligations
     guaranteed hereby until payment in full of all obligations guaranteed
     hereby.

          (g) As between the Guarantors, on the one hand, and the Holders and
     the Trustee, on the other hand, (x) the maturity of the obligations
     guaranteed hereby may be accelerated as provided in Article 6 of the
     Indenture for the purposes of this Note Guarantee, notwithstanding any
     stay, injunction or other prohibition preventing such acceleration in
     respect of the obligations guaranteed hereby, and (y) in the event of any
     declaration of acceleration of such obligations as provided in Article 6 of
     the Indenture, such obligations (whether or note due and payable) shall
     forthwith become due and payable by the Guarantors for the purpose of this
     Note Guarantee.

          (h) The Guarantors shall have the right to seek contribution from any
     non-paying Guarantor so long as the exercise of such right does not impair
     the rights of the Holders under the Guarantee.


                                       2

<PAGE>

          (i) Pursuant to Section 11.02 of the Indenture, after giving effect to
     any maximum amount and any other contingent and fixed liabilities that are
     relevant under any applicable Bankruptcy or fraudulent conveyance laws, and
     after giving effect to any collections from, rights to receive contribution
     from or payments made by or on behalf of any other Guarantor in respect of
     the obligations of such other Guarantor under Article 11 of the Indenture,
     this new Note Guarantee shall be limited to the maximum amount permissible
     such that the obligations of such Guarantor under this Note Guarantee will
     not constitute a fraudulent transfer or conveyance.

     3. Execution and Delivery. Each Guaranteeing Subsidiary agrees that the
Note Guarantees shall remain in full force and effect notwithstanding any
failure to endorse on each Note a notation of such Note Guarantee.

     4. Guaranteeing Subsidiary May Consolidate, Etc. on Certain Terms.

          (a) The Guaranteeing Subsidiary may not consolidate with or merge with
     or into (whether or not such Guarantor is the surviving Person) another
     corporation, Person or entity whether or not affiliated with such Guarantor
     unless:

               (i) subject to Sections 11.04 and 11.05 of the Indenture, the
          Person formed by or surviving any such consolidation or merger (if
          other than a Guarantor or the Company) unconditionally assumes all the
          obligations of such Guarantor, pursuant to a supplemental indenture in
          form and substance reasonably satisfactory to the Trustee, under the
          Notes, the Indenture and the Note Guarantee on the terms set forth
          herein or therein; and

               (ii) immediately after giving effect to such transaction, no
          Default or Event of Default exists.

          (b) In case of any such consolidation, merger, sale or conveyance and
     upon the assumption by the successor corporation, by supplemental
     indenture, executed and delivered to the Trustee and satisfactory in form
     to the Trustee, of the Note Guarantee endorsed upon the Notes and the due
     and punctual performance of all of the covenants and conditions of the
     Indenture to be performed by the Guarantor, such successor corporation
     shall succeed to and be substituted for the Guarantor with the same effect
     as if it has been named herein as a Guarantor. Such successor corporation
     thereupon may cause to be signed any or all of the Note Guarantees to be
     endorsed upon all of the Notes issuable hereunder which theretofore shall
     not have been signed by the Company and delivered to the Trustee. All the
     Note Guarantees so issued shall in all respects have the same legal rank
     and benefit under the Indenture as the Note Guarantees theretofore and
     thereafter issued in accordance with the terms of the Indenture as though
     all of such Note Guarantees had been issued at the date of the execution
     hereof.

          (c) Except as set forth in Articles 4 and 5 and Section 11.05 of
     Article 11 of the Indenture, and notwithstanding clauses (a) and (b) above,
     nothing contained in the Indenture or in any of the Notes shall prevent any
     consolidation or merger of a Guarantor with or into the Company or another
     Guarantor, or shall prevent any sale or conveyance


                                       3

<PAGE>

     of the property of a Guarantor as an entirety or substantially as an
     entirety to the Company or another Guarantor.

     5. Releases.

          (a) In the event of a sale or other disposition of all of the assets
     of any Guarantor, by way of merger, consolidation or otherwise, or a sale
     or other disposition of all to the capital stock of any Guarantor, in each
     case to a Person that is not (either before or after giving effect to such
     transaction) a Restricted Subsidiary of the Company, then such Guarantor
     (in the event of a sale or other disposition, by way of merger,
     consolidation or otherwise, of all of the capital stock of such Guarantor)
     or the corporation acquiring the property (in the event of a sale or other
     disposition of all or substantially all of the assets of such Guarantor)
     will be released and relieved of any obligations under its Note Guarantee;
     provided that the Net Proceeds of such sale or other disposition are
     applied in accordance with the applicable provisions of the Indenture,
     including without limitation Section 4.10 of the Indenture. Upon delivery
     by the Company to the Trustee of an Officers' Certificate and an Opinion of
     Counsel to the effect that such sale or other disposition was made by the
     Company in accordance with the provisions of the Indenture, including
     without limitation Section 4.10 of the Indenture, the Trustee shall execute
     any documents reasonably required in order to evidence the release of any
     Guarantor from its obligations under its Note Guarantee.

          (b) Any Guarantor not released from its obligations under its Note
     Guarantee shall remain liable for the full amount of principal of and
     interest on the Notes and for the other obligations of any Guarantor under
     the Indenture as provided in Article 11 of the Indenture.

     6. No Recourse Against Others. No past, present or future director,
officer, employee, incorporator, stockholder or agent of the Guaranteeing
Subsidiary, as such, shall have any liability for any obligations of the Company
or any Guaranteeing Subsidiary under the Notes, any Note Guarantees, the
Indenture or this Supplemental Indenture or for any claim based on, in respect
of, or by reason of, such obligations or their creation. Each Holder of the
Notes by accepting a Note waives and releases all such liability. The waiver and
release are part of the consideration for issuance of the Notes. Such waiver may
not be effective to waive liabilities under the federal securities laws and it
is the view of the SEC that such a waiver is against public policy.

     7. NEW YORK LAW TO GOVERN. THE INTERNAL LAW OF THE STATE OF NEW YORK SHALL
GOVERN AND BE USED TO CONSTRUE THIS SUPPLEMENTAL INDENTURE BUT WITHOUT GIVING
EFFECT TO APPLICABLE PRINCIPLES OF CONFLICTS OF LAW TO THE EXTENT THAT THE
APPLICATION OF THE LAWS OF ANOTHER JURISDICTION WOULD BE REQUIRED THEREBY.

     8. Counterparts. The parties may sign any number of copies of this
Supplemental Indenture. Each signed copy shall be an original, but all of them
together represent the same agreement.


                                       4

<PAGE>

     9. Effect of Headings. The Section headings herein are for convenience only
and shall not affect the construction hereof.

     10. The Trustee. The Trustee shall not be responsible in any manner
whatsoever for or in respect of the validity or sufficiency of this Supplemental
Indenture or for or in respect of the recitals contained herein, all of which
recitals are made solely by the Guaranteeing Subsidiary and the Company.

     IN WITNESS WHEREOF, the parties hereto have caused this Supplemental
Indenture to be duly executed and attested, all as of the date first above
written.

     Dated: March 11, 2002

                           GEORGIA PCS MANAGEMENT, LLC

                           By:
                              -------------------------------------------------
                                    Name:
                                         --------------------------------------
                                    Title:
                                          -------------------------------------


                            GEORGIA PCS LEASING, LLC

                            By:
                               ------------------------------------------------
                                     Name:
                                          -------------------------------------
                                     Title:
                                           ------------------------------------


                            US UNWIRED, INC.


                            By:
                               ------------------------------------------------
                                     Name:
                                          -------------------------------------
                                     Title:
                                           ------------------------------------


                            LOUISIANA UNWIRED, LLC


                            By:
                               ------------------------------------------------
                                     Name:
                                          -------------------------------------
                                     Title:
                                           ------------------------------------


                                       5

<PAGE>

                            UNWIRED TELECOM CORP.


                            By:
                               ------------------------------------------------
                                     Name:
                                          -------------------------------------
                                     Title:
                                           ------------------------------------


                           STATE STREET BANK AND TRUST
                               COMPANY, as Trustee

                               By:
                                  ---------------------------------------------
                                        Authorized Signatory




                                       6

<PAGE>

                                    GUARANTEE

     For value received, each Guarantor (which term includes any successor
Person under the Indenture) has, jointly and severally, unconditionally
guaranteed, to the extent set forth in the Indenture and subject to the
provisions in the Indenture dated as of October 29, 1999 (the "Indenture") among
US Unwired Inc., the Guarantors listed on Schedule I thereto and State Street
Bank and Trust Company, as trustee (the "Trustee"), (a) the due and punctual
payment of the principal of, premium, if any, interest and Liquidated Damages,
if any, on the Notes (as defined in the Indenture), whether at maturity, by
acceleration, redemption or otherwise, the due and punctual payment of interest
on overdue principal and premium, and, to the extent permitted by law, interest,
and the due and punctual performance of all other obligations of the Company to
the Holders or the Trustee all in accordance with the terms of the Indenture and
(b) in case of any extension of time of payment or renewal of any Notes or any
of such other obligations, that the same will be promptly paid in full when due
or performed in accordance with the terms of the extension or renewal, whether
at stated maturity, by acceleration or otherwise. The obligations of the
Guarantors to the Holders of Notes and to the Trustee pursuant to the Note
Guarantee and the Indenture are expressly set forth in Article 11 of the
Indenture and reference is hereby made to the Indenture for the precise terms of
the Note Guarantee. Each Holder of a Note, by accepting the same, (a) agrees to
and shall be bound by such provisions, (b) authorizes and directs the Trustee,
on behalf of such Holder, to take such action as may be necessary or appropriate
to effectuate the subordination as provided in the Indenture and (c) appoints
the Trustee attorney-in-fact of such Holder for such purpose; provided, however,
that the Indebtedness evidenced by this Note Guarantee shall cease to be so
subordinated and subject in right of payment upon any defeasance of this Note in
accordance with the provisions of the Indenture.

                                  LOUISIANA UNWIRED, LLC


                                  By:
                                     ------------------------------------------
                                           Name:
                                                -------------------------------
                                           Title:
                                                 ------------------------------


                                  UNWIRED TELECOM CORP.


                                  By:
                                     ------------------------------------------
                                           Name:
                                                -------------------------------
                                           Title:
                                                 ------------------------------

<PAGE>

                           GEORGIA PCS MANAGEMENT, LLC

                                 By:
                                    -------------------------------------------
                                          Name:
                                               --------------------------------
                                          Title:
                                                -------------------------------


                            GEORGIA PCS LEASING, LLC

                                 By:
                                    -------------------------------------------
                                          Name:
                                               --------------------------------
                                          Title:
                                                -------------------------------