<PAGE>   1
                                                                    EXHIBIT 10.2

                    ----------------------------------------

                          PHONETEL TECHNOLOGIES, INC.,
                                   As Issuer,

                            THE SUBSIDIARY GUARANTORS
                           Named on Schedule I hereto

                                       AND

                              MARINE MIDLAND BANK,
                                   As Trustee

                          -----------------------------

                          SECOND SUPPLEMENTAL INDENTURE

                            Dated as of May 29, 1997

                       Supplementing the Indenture, Dated
                    as of December 18, 1996, as supplemented
                       by the First Supplemental Indenture
                       dated as of January 3, 1997, among
                        PhoneTel Technologies, Inc., the
                         Subsidiary Guarantors named on
                             Schedule I thereto and
                         Marine Midland Bank, as Trustee

                          -----------------------------

                                  $125,000,000

                            12% SENIOR NOTES DUE 2006

                    ----------------------------------------
 


<PAGE>   2



                  THIS SECOND SUPPLEMENTAL INDENTURE, dated as of May 29, 1997
(the "Second Supplemental Indenture"), is by and among (i) PHONETEL
TECHNOLOGIES, INC., an Ohio corporation (the "Company"), as issuer of the 12%
Senior Notes due 2006 (the "Notes"), (ii) each Subsidiary of the Company
existing on the date of this Second Supplemental Indenture as set forth on
Schedule I hereto and each of the Company's Subsidiaries which becomes a
guarantor of the Notes in compliance with Section 4.15 of the Indenture referred
to herein in which such Subsidiary agrees to be bound by the terms of the
Indenture, as guarantors of the Company's obligations under the Indenture and
the Notes (each, a "Subsidiary Guarantor"), and (iii) Marine Midland Bank, as
trustee (the "Trustee").

                  WHEREAS, the Company, the Subsidiary Guarantors as of December
18, 1996 (the "Issue Date") and the Trustee heretofore executed and delivered an
Indenture, dated as of December 18, 1996 (the "Original Indenture"); and

                  WHEREAS, pursuant to the Original Indenture the Company issued
and the Trustee authenticated and delivered $125 million aggregate principal
amount of the Notes, which Notes were guaranteed by each of the Company's
Subsidiaries listed on Schedule I to the Original Indenture; and

                  WHEREAS, on January 3, 1997, the Company's subsidiary,
PhoneTel CCI, Inc., a Texas corporation, was merged with and into Cherokee
Communications, Inc., a Texas corporation ("Cherokee"), with Cherokee being the
surviving corporation (the "Cherokee Merger"), and as a result of the Cherokee
Merger, Cherokee and its two wholly owned subsidiaries, Cherokee Communications,
Inc., a South Dakota corporation, and Cherokee Communications, Inc., a Nevada
corporation, each became a Subsidiary of the Company and entered into the First
Supplemental Indenture, dated as of January 3, 1997 (the "First Supplemental
Indenture" and, together with the Original Indenture, the "Indenture"), among
the Company, the Trustee and the Subsidiary Guarantors set forth on Schedule I
thereto; and

                  WHEREAS, Section 4.15 of the Indenture provides that the
Company shall cause each Subsidiary of the Company formed or acquired after the
Issue Date to issue a Subsidiary Guarantee and to execute and deliver an

 

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<PAGE>   3



indenture supplemental to the Indenture as a Subsidiary Guarantor; and

                  WHEREAS, on March 4, 1997, the Company formed its wholly owned
subsidiary, PhoneTel Acquisition Corp., a Georgia corporation ("PhoneTel
Acquisition"), and on April 3, 1997, the Company formed its wholly owned
subsidiary, PhoneTel V, Inc., a Georgia corporation ("PhoneTel V"); and

                  WHEREAS, Section 9.01 of the Indenture provides that the
Company, the Subsidiary Guarantors and the Trustee may amend the Indenture
without the consent of any Holder of the Notes in order to add additional
Subsidiary Guarantors pursuant to Section 4.15 of the Indenture; and

                  WHEREAS, this Second Supplemental Indenture has been duly
authorized by all necessary corporate action on the part of the Company and the
Subsidiary Guarantors.

                  NOW, THEREFORE, the Company, the Subsidiary Guarantors listed
on Schedule I hereto and the Trustee agree as follows for the equal and ratable
benefit of each other and the Holders of the Notes:

                                    ARTICLE I
                        ADDITION OF SUBSIDIARY GUARANTORS

                  SECTION 1.1. ADDITION OF SUBSIDIARY GUARANTORS. Each of
PhoneTel Acquisition and PhoneTel V hereby expressly agrees to issue a
Subsidiary Guarantee and to be bound as, and assume the obligations of, a
Subsidiary Guarantor under the Indenture, including without limitations the
obligations set forth in Article X of the Indenture.

                  SECTION 1.2. TRUSTEE'S ACCEPTANCE. The Trustee hereby
accepts this Second Supplemental Indenture and agrees to perform the same under
the terms and conditions set forth in the Indenture.

 

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<PAGE>   4




                                   ARTICLE II
                                  Miscellaneous
                                  -------------

                  SECTION 2.1. EFFECT OF SUPPLEMENTAL INDENTURE. Upon the
execution and delivery of this Second Supplemental Indenture by the Company, the
Subsidiary Guarantors listed in Schedule I hereto and the Trustee, the Indenture
shall be supplemented in accordance herewith, and this Second Supplemental
Indenture shall form a part of the Indenture for all purposes, and every Holder
of Notes heretofore or hereafter authenticated and delivered under the Indenture
shall be bound thereby.

                  SECTION 2.2. INDENTURE REMAINS IN FULL FORCE AND EFFECT.
Except as supplemented hereby, all provisions in the Indenture shall remain in
full force and effect.

                  SECTION 2.3. INDENTURE AND SUPPLEMENTAL INDENTURE CONSTRUED
TOGETHER. This Second Supplemental Indenture is an indenture supplemental to and
in implementation of the Indenture, and the Indenture and this Second
Supplemental Indenture shall henceforth be read and construed together.

                  SECTION 2.4. CONFIRMATION AND PRESERVATION OF INDENTURE. The
Indenture as supplemented by this Second Supplemental Indenture is in all
respects confirmed and preserved.

                  SECTION 2.5. CONFLICT WITH TRUST INDENTURE ACT. If any
provision of this Second Supplemental Indenture limits, qualifies or conflicts
with any provision of the TIA that is required under the TIA to be part of and
govern any provision of this Second Supplemental Indenture, the provision of the
TIA shall control. If any provision of this Second Supplemental Indenture
modifies or excludes any provision of the TIA that may be so modified or
excluded, the provision of the TIA shall be deemed to apply to the Indenture as
so modified or to be excluded by this Second Supplemental Indenture, as the case
may be.

 

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<PAGE>   5




                  SECTION 2.6. SEVERABILITY. In case any provision in this
Second Supplemental Indenture shall be invalid, illegal or unenforceable, the
validity, legality and enforceability of the remaining provisions shall not in
any way be affected or impaired thereby.

                  SECTION 2.7. TERMS DEFINED IN THE INDENTURE. All capitalized
terms not otherwise defined herein shall have the meanings ascribed to them in
the Indenture.

                  SECTION 2.8. HEADINGS. The Article and Section headings of
this Second Supplemental Indenture have been inserted for convenience of
reference only, are not to be considered a part of this Second Supplemental
Indenture and shall in no way modify or restrict any of the terms or provisions
hereof.

                  SECTION 2.9. BENEFITS OF SECOND SUPPLEMENTAL INDENTURE, ETC.
Nothing in this Second Supplemental Indenture or the Notes, express or implied,
shall give to any Person, other than the parties hereto and thereto and their
successors hereunder and thereunder and the Holders of the Notes, any benefit of
any legal or equitable right, remedy or claim under the Indenture, this Second
Supplemental Indenture or the Notes.

                  SECTION 2.10. SUCCESSORS. All agreements of the Company and
the Subsidiary Guarantors in this Second Supplemental Indenture shall bind their
respective successors. All agreements of the Trustee in this Second Supplemental
Indenture shall bind its successors.

                  SECTION 2.11. TRUSTEE NOT RESPONSIBLE FOR RECITALS. The
recitals contained herein shall be taken as the statements of the Company and
the Subsidiary Guarantors, and the Trustee assumes no responsibility for their
correctness. The Trustee shall have no liability for the validity or sufficiency
of this Second Supplemental Indenture.

                  SECTION 2.12. CERTAIN DUTIES AND RESPONSIBILITIES OF THE
TRUSTEE. In entering into this Second Supplemental Indenture, the Trustee shall
be entitled to the benefit of every provision of the Indenture relating to the
conduct or affecting the liability or affording

 

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<PAGE>   6



protection to the Trustee, whether or not elsewhere herein so provided.

                  SECTION 2.13. GOVERNING LAW. This Second Supplemental
Indenture shall be governed by, and construed in accordance with, the laws of
the State of New York 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.

                  SECTION 2.14. COUNTERPART ORIGINALS. The parties may sign any
number of copies of this Second Supplemental Indenture. Each signed copy shall
be an original, but all of them together represent the same agreement.

 

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<PAGE>   7



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

                                            THE COMPANY:
                                            ------------

                                            PHONETEL TECHNOLOGIES, INC.

                                       By:  /s/ T.L. Martin
                                            ----------------------------------
                                            Name: Tammy L. Martin
                                            Title: Executive Vice
                                                     President

 

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<PAGE>   8



                                            THE SUBSIDIARY GUARANTORS:
                                            --------------------------

                                            PUBLIC TELEPHONE CORPORATION
                                            WORLD COMMUNICATIONS, INC.
                                            PARAMOUNT COMMUNICATION SYSTEMS,
                                              INC.
                                            NORTHERN FLORIDA TELEPHONE
                                              CORPORATION
                                            PAYPHONES OF AMERICA, INC.
                                            CHEROKEE COMMUNICATIONS, INC.
                                              (a Texas corporation and as
                                              successor by merger with
                                              PHONETEL CCI, INC.)
                                            CHEROKEE COMMUNICATIONS, INC.
                                              (a South Dakota corporation)
                                            CHEROKEE COMMUNICATIONS, INC.
                                              (a Nevada corporation)
                                            PHONETEL ACQUISITION CORP.
                                            PHONETEL V, INC.

                                            For each of the above:

                                       By:  /s/ T.L. Martin
                                           ---------------------------------
                                           Name: Tammy L. Martin
                                           Title: Executive Vice
                                                    President

 

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<PAGE>   9




                                            MARINE MIDLAND BANK,
                                               as Trustee

                                       By: /s/ Marcia Markowski
                                           --------------------------------
                                           Name: Marcia Markowski
                                           Title: Corporate Trust Officer

 

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<PAGE>   10


                                   Schedule I

                              Subsidiary Guarantors
                              ---------------------

<TABLE>
<CAPTION>
Name of Subsidiary                                                     Jurisdiction of
------------------                                                     ---------------
                                                                       Incorporation
                                                                       -------------
<S>    <C>                                                          <C>
1.       Public Telephone Corporation                                  Indiana

2.       World Communications, Inc.                                    Missouri

3.       Paramount Communication
           Systems, Inc.                                               Florida

4.       Northern Florida Telephone
           Corporation                                                 Florida

5.       Payphones of America, Inc.                                    Ohio

6.       Cherokee Communications, Inc.                                 Texas

7.       Cherokee Communications, Inc.                                 South Dakota

8.       Cherokee Communications, Inc.                                 Nevada

9.       PhoneTel Acquisition Corp.                                    Georgia

10.      PhoneTel V, Inc.                                              Georgia
</TABLE>

 

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