I bought my iPhone 4S on the phone with AT&T and added a new line to get the subsidized price. After only 2 days I have 12GB left on my 32GB iPhone 4S. With all these awesome games I really think I'll need more storage. Would it be possible to exhange my current 4S at an AT&T store for the 64GB model and still get it at the subsidized price? Let me know! Thanks.