The network, the smallest in the UK, is also launching a new tariff scheme this week which may start a price war among the nation's mobile operators.
The decision to rebrand was taken in response to increasing demand for global services. T-Mobile has 40m customers worldwide and owns network operators in Germany, the UK, Austria and the Czech Republic. It also holds significant interests in the Netherlands, Russia and Poland.
One 2 One was known as Mercury One 2 One before its acquisition by Deutsche Telekom in 1999 for £8.4bn from Cable & Wireless. It has around 7m customers in the UK, as well as carrying around 1m subscribers to the Virgin Mobile network.
News of the rebranding coincides with that of larger operator BT Cellnet, which is being rebranded as O2.