求教，先谢谢各位了！
purchase a new device with T-Mobile on a qualifying postpaid Simple Choice
plan (you would not be able to sign up for a T-Mobile prepaid or Simple
Choice Family Plan with no credit check）
如果想换成prepaid怎么办？
The amount paid will not be more than the ETF amount the customers’
previous carriers charge for the type of device traded-in
如果用不在current plan的烂手机去trade in，那不是跟那个final bill上的手机不一
样吗，Tmobile会不会拒付ETF呢？
再者，现在的plan中的ATT手机交了ETF就能马上解锁？想继续用这个手机而不是新买的
Tmobile的手机 prepaid怎么办？
