Despite T-Mobile USA being very comfortable with prepaid service, it hasn't jumped in with both feet like its potential partner MetroPCS or its arch-rival Sprint. The company has just confirmed to FierceWireless that it's not waiting for a merger to experiment further; it's currently trialing GoSmart Mobile, a prepaid-only network that uses data speed, not caps, as the incentive to jump to higher tiers. Paying $30 per month offers unlimited calling a
