The T-Mobile and MetroPCS merger has officially completed and both companies now operate under the T-Mobile US brand. MetroPCS brings its 9 million customers to join T-Mobile's 34 million. The new entity will be traded on the New York Stock Exchange as TMUS.Even with the merger T-Mobile still holds the fourth place behind Verizon, AT&T and Sprint with a total of 43 million customers.
The plan of the new entity is to gradually merge Metro PCS with T-Mobile's base and the entire process is expected to be completed by 2015. Meanwhile the Metro PCS spectrum will be used to expand T-Mobile's LTE network.
source - The Verge