I am looking to sell my AT&T iPhone 5. I will be switching back to Sprint because LTE was just turned on in the areas I am in. \ My question is: if I simply port my number to Sprint (thus terminating my service with AT&T), can I turn around and sell the AT&T iPhone 5 to help pay for the ETF? Or do I need to activate a crappy phone on my AT&T account first, then cancel (freeing up my iPhone 5)? I know with Verizon and Sprint you can't since the ESN is locked on the account.