BTW, the reason why for all of this has to do with the fact that Verizon and AT&T bought up the old A & B side cellular (850 MHz) carriers that had been operating since the 1980s and had built their networks when cellular service was duopolistic and calls cost 50¢/min. T-Mobile was build on ~2 GHz PCS licenses which require about 4-5x the number of towers to cover the same area as 850 MHz. For this reason they focused on covering cities. With T-Mobile's GSM-based technology it is more difficult to restrict roaming than with Sprint's CDMA technology. Sprint can set the phone to not allow roaming if it can receive a Sprint signal. T-Mobile has to restrict roaming based on groups of cells that cover various geographic areas. It's a crude tool at best.
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