Reverse Corp, which provides reverse calling services and operates payphone brand TriTel, said it had extended the term of its agreement with Telstra for a further five years.
Under the new arrangement, Telstra's mobile subscribers will be able to use the 1800-REVERSE service from December.
The deal also covers billing for reverse charge calls to Telstra mobiles, and management of Telstra's reverse charge products using the Reverse Corp platform.
Reverse Corp and Telstra have been in talks to hammer out the terms of the agreement since February 2010.
The companies have this year announced four separate short-term extensions on their existing fixed-line service agreement while talks continued.
As well as Australia, the company offers reverse charges services in the UK and the Republic of Ireland, and is pursuing an expansion into Spain.
Reverse Corp CEO Paul Jobbins last month tentatively forecast a return to profit growth in FY12 after a run of declines.
REF shares stayed unchanged on Thursday at $0.038.