IPhone With Prepaid Plan at AT&T?

Can anyone help?

My friend gave me her brand new IPhone to use before she moved back to Europe. This IPhone has the At&T sim card in it. I currently have Tmobile "Pay as you go" plan, where I pay only $50 and get unlimited everything. I went to the local At&T store to see if I could get the same plan with them and use the new IPhone. The guy basically told me to go to hell and didn't even bother trying to explain to me why this wouldn't be possible. I heard that At&T does offer prepaid plans for IPhones… Is anyone familiar with this? I'm a student and it would be tough for me to pay $120/month for the typical IPhone plan.

The guy at at&t didn't explain it to you well because they barely make any money from a customer who wants to get a prepaid plan or w.e that's why he probably didn't wanna waste his time explaining it to you.they're a**holes