Exhibit 4.5

TENTH AMENDMENT TO

MANAGEMENT SERVICES AGREEMENT

Between

AT&T MEXICO, INC.

A
corporation duly organized under the laws of the State of Delaware, United States of America, with headquarters in Wilmington, Delaware, USA, hereinafter AT&T MEXICO, with Permanent Establishment in the United Mexican States.
Establishment in the terms provided in the Income Tax Law with address at Parque Via 190-12th floor, Colonia Cuauhtémoc, 06599, Mexico City, D.F.

And

AMÉRICA MÓVIL, S.A.B. DE C.V.

A sociedad anónima bursátil de capital variable duly organized under the laws of the United Mexican States, with its principal place
of business in Mexico City, D.F., hereinafter AMÉRICA MÓVIL.



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This TENTH AMENDMENT TO MANAGEMENT SERVICES AGREEMENT is made as of August 3, 2010
(the Amendment), between AT&T MEXICO and AMÉRICA MÓVIL.

WHEREAS, AT&T MEXICO and
AMÉRICA MÓVIL entered into that certain Management Services Agreement dated February 27, 2002 as amended by that certain First Amendment to Management Services Agreement dated as of January 1, 2003; that certain Second
Amendment to Management Services Agreement dated as of October 29, 2003; that certain Third Amendment to Management Services Agreement dated as January 1, 2004; that certain Fourth Amendment to Management Services Agreement dated as of
January 31, 2005; that certain Fifth Amendment to Management Services Agreement dated as of December 31, 2005; that certain Sixth Amendment to Management Services Agreement dated as of February 1, 2007, that certain Seventh Amendment
to Management Services Agreement dated as of July 7, 2010, that certain Eighth Amendment to Management Services Agreement dated as of September 23, 2009, and that certain Ninth Amendment to Management Services Agreement dated as of
November 18, 2009 (as amended, the MSA).

WHEREAS, AT&T MEXICO and AMÉRICA MÓVIL desire to
amend the MSA as provided herein.

NOW, THEREFORE, in consideration of the premises and the mutual agreements and covenants
hereinafter set forth, the parties hereto hereby agree as follows:

SECTION 1. The parties acknowledge that in compensation
for services rendered by AT&T MEXICO under the MSA for the eighth year (2009) of the term thereto, AMÉRICA MÓVIL paid AT&T MEXICO in 2009 SEVEN AND A HALF MILLION US DOLLARS (US $7,500,000.00), in twelve monthly
installments of SIX HUNDRED TWENTY-FIVE THOUSAND US DOLLARS (US $625,000.00), plus value added tax.

SECTION 2. In accordance
with the terms of Clause FOURTH of the MSA, AMÉRICA MÓVIL shall pay AT&T MEXICO SEVEN AND A HALF MILLION US DOLLARS (US $7,500,000.00) plus value added tax, for the ninth year (2010) of the term of the MSA in



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compensation for services rendered by AT&T MEXICO thereunder. AMÉRICA MÓVIL shall make this SEVEN AND A HALF MILLION US DOLLAR (US $7,500,000.00) payment to AT&T MEXICO in
twelve monthly installments of SIX HUNDRED TWENTY-FIVE THOUSAND US DOLLARS (US $625,000.00), plus value added tax, through wire transfer of immediately available funds payable in United States Dollars to a bank account designated by AT&T MEXICO
(which monthly payments commenced in January 2009). No later than the end of November 2010, the parties shall begin consultations and use best efforts to agree on compensation to be paid to AT&T MEXICO for the remaining term of the MSA.

SECTION 3. This Amendment and the MSA are hereby confirmed as being in full force and effect.

SECTION 4. This Amendment may be executed in one or more counterparts, and by the different parties hereto in separate counterparts, each
of which when executed shall be deemed to be an original but all of which taken together shall constitute one and the same agreement.

SECTION 5. For interpretation and fulfillment of this Amendment, the parties expressly agree to submit to the laws of the territory and courts of Mexico City, D.F., waiving the application of any other
law or jurisdiction of any court that might have jurisdiction over them by reason of their current or future address.

This
agreement is entered in Mexico City, D.F., on the date first set forth above.



|                                                                    |  |  |  |                                                                        
|------------------------------------------------------------------- |  |  |  | -----------------------------------------------------------------------
|AT&T MEXICO, INC.                                                   |  |  |  | AMÉRICA MÓVIL, S.A.B. DE C.V.                                          
|                                                                    |  | 
|/s/ Michael Bowling By: Michael Bowling President AT&T Mexico, Inc. |  |  |  | /s/ Alejandro Cantú Jiménez By: Alejandro Cantú Jiménez General Counsel



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