The UK's fourth-largest mobile phone operator has shifted its lobbying account out of Politics Direct following a competitive pitch.
Mandate has been briefed to support T-Mobile's ongoing activity in the UK as the merger takes shape, providing strategic political advice, intelligence and issues monitoring, as well as wider public affairs support.
Europe's top competition watchdog approved the proposed merger of Orange and T-Mobile in the UK earlier this month, after obtaining concessions from the operators' parent companies.
The joint venture between France Telecom's Orange UK and Deutsche Telekom's T-Mobile UK is due to start trading in April and will be Britain's largest mobile operator.
T-Mobile UK head of public affairs Richard Rumbelow said: '2010 will be an important year in the commercial future for T-Mobile, with the merger with Orange UK, the delivery of a digital economy and our future relationships following the wider political and government changes.'
He added: 'Mandate provided a fresh perspective in dealing with these challenges, and in addition it has experience with clients who have undertaken culture change programmes.'
Meanwhile, Orange continues to use Open Road as its retained public affairs adviser. Open Road won the Orange account from FD-LLM in 2008.