If i just got an AT&T contract can i still switch to straight talk?

I just ordered the iphone 5 from AT&T and then discovered straight talk and was wondering if i could switch to it even though i'm in contract. If so please let me know how to go about doing this. Will i still have to pay AT&T if i do switch to straight talk? Will i get my deposit back that i gave to AT&T when i signed up? Please let me know all details! I really want the unlimited data from straight talk that i won't get with AT&T!

Straight Talk limits your data plan. If you use over 2 to 4GB of data per month you will be told to stop using so much data or your service will be shut off.

Unless you don't want the IPhone I would keep AT&T. If you cancel your AT&T plan you will be charged for the entire cost of the phone.