Buying a 2 year old used AT&T Samsung Galaxy s3 4g LTE could I get service through T-Mobile on it?

[Ashley A]

The guy that's selling it said he got it brand new 2 years ago on an AT&T contract and just upgraded to a new phone a week ago and works fine. He only wants $50 for it, which is good for me financially. I've never had service through them, I always use T-Mobile. I learned that T-Mobile and at&t use the same type of cell tower so I could put a T-Mobile sim card in it and it will be fine but some things about the service might not work well depending on the cell phone. I'm going to be on a prepaid plan. Anyone have any problems?