Can i buy a At&t prepaid phone at walmart and buy a iphone 4s on ebay or amazon, and switch sim cards?

Well if Mike told you to ignore whodatman then ignore him also. AT&T iPhones do have a micro SIM card in them. If you buy a cheap GoPhone at Walmart they'll know which phone you have activated. Besides, you need to purchase the iPhone specifically for AT&T and you won't be able to activate it without having a data plan. Don't waste your time or money. If you can swing a contract plan with AT&T you can get a brand new iPhone3gs for $1. Just pay your bills and you'll have a brand new iPhone. Hope it helps and good luck.

Ignore whodatman. You can buy the unlocked version of the iPhone 4S for its full retail price, and it runs on GSM networks so you could certainly put a microSIM card should AT&T have any prepaid ones available; they can do it all for you at an AT&T store. If AT&T doesn't have microSIM cards, T-Mobile offers a $30 prepaid plan that gives 100 minutes, unlimited messages, and unlimited data (5GB of which will operate at full 3G speed).

If you've prepaid SIM, then you can just cut it and put it in the iPhone. You don't need to unlock the iPhone if it's AT&T. If you need iPhone 4S without contract cheaper, you can mail me to [email protected]