Though I alread have (and am quite happy with) my 32GB 4S, I've been offered a NIB 16GB 4S as a trade for a MacBook I'm selling. The seller is planning to get one using an upgrade on his account and doesn't want the phone themselves- but I'm curious as to what problems that this could potentially cause for whoever gets the phone (whoever I sell/trade/give it to). When the phone is activated, won't it activate under the number it was originally bought for? I'm sure there has to be a way to deal with this otherwise people couldn't/wouldn't be selling/buying all the phones that they pre-ordered, but I just want to confirm before I go forward so I don't end up getting burned (or burning someone unintentionally...). Thanks!