IPhone 5s to LG Expression 395

I would like to switch my phone over from the iPhone 5s to the LG Expression 395. I have done some research and found that to switch a phone you just remove the SIM card and put it on the other phone. Though with these two phones they use different SIM cards. If I bought the LG Expression without a contract on Amazon and took it into an AT&T store, would they provide a new SIM card and make it work for the new phone? Would it cost anything?