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(From the website)
We touched on this in the wrap-up of this mornings AT&T Press call but apparently it's causing such a stir we're going to try and clarify a few things:
With AT&T planning to use T-Mobile's existing 1700 MHz spectrum for future LTE rollouts, AT&T execs are saying that T-Mobile customers will have to replace their current 3G/4G phones once the merger is completed. This will be a mandatory upgrade unless of course you want your phone to work on edge only.