i currently have an ATT account that i'm out of contract/upgrade eligible. i want to switch to Verizon as i started working at their HQ recently and get a nice discount. the iPhone 5s/c is not available to employee discount accounts until adequate supply is available (took almost 4 months for the iPhone 5) i want to buy the iPhone 5s with my upgrade through ATT and then cancel my plan and pay the ETF. once i do that can i use that same phone on Verizon's network?