Radio Shack is ending its partnership with T-Mobile in favor of a new one with Verizon, which will be joining current partners AT&T and Sprint. If you want a T-Mobile phone or service plan at Radio Shack the last day to get one is September 14th.
The next day Verizon moves in and setting up shop the very next day. The partnership with T-mobile was apparently unprofitable and also a very rocky relationship. Better get that T-Mobile phone from the Shack now.