Exhibit 10.23H

Pages where confidential treatment has been requested are stamped “Confidential Treatment Requested and

the Redacted Material has been separately filed with the Commission,” and places where information has

been redacted have been marked with (***).

FIFTEENTH AMENDMENT

TO THE

CSG MaSTER SUBSCRIBER MANAGEMENT SYSTEM AGREEMENT

BETWEEN

CSG SYSTEMS, INC.

AND

DISH NETWORK, L.L.C.

THIS FIFTEENTH AMENDMENT (this “Amendment”) is made by and between CSG Systems, Inc., a Delaware corporation (“CSG”), and DISH Network L.L.C., a Colorado limited liability company (“Customer”). This amendment shall be effective as of the date last signed below (the “Effective Date”). CSG and Customer entered into a certain CSG Master Subscriber Management System Agreement (Document #2301656) effective as of January 1, 2010 (the “Agreement”), and now desire to further amend the Agreement in accordance with the terms and conditions set forth in this Amendment. If the terms and conditions set forth in this Amendment shall be in conflict with the Agreement, the terms and conditions of this Amendment shall control. Any terms in initial capital letters or all capital letters used as a defined term but not defined in this Amendment shall have the meaning set forth in the Agreement. Upon execution of this Amendment by the parties, any subsequent reference to the Agreement between the parties shall mean the Agreement as amended by this Amendment. Except as amended by this Amendment, the terms and conditions set forth in the Agreement shall continue in full force and effect according to their terms.

CSG and Customer agree as follows as of the Effective Date:

Interactivate. Interactivate, utilized in CSG’s managed services environment, provides real-time, bi-directional, transaction processing and event management. Interactivate provides the link between subscribers and services, enabling customers to launch new services and streamline processes.

At the core of the Product are adapters that enable communication with upstream business systems and downstream systems. The work-flow engine with its graphical user interface and drag-and-drop capabilities allows for implementation of specific business rules.

CSG Licensed Products

III. CSG’s Interactivate

Note 1: Implementation and Configuration. All implementation and configuration services and the associated fees shall be set forth in a mutually agreed upon statement(s) of work. Reimbursable Expenses are additional.

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All fees provided herein are subject to annual adjustment as provided in Section 4 of the Agreement.

IN WITNESS WHEREOF the parties hereto have caused this Amendment to be executed by their duly authorized representatives.