Can I use my Verizon iPhone 5 on AT&T?

I bought an iPhone 5 this past friday (september 21) from a verizon store because my usual carrier (at&t) was sold out. Apparently the verizone iphone 5s are unlocked.So, could I cancel my two year contract with verizon (just opened three days ago, so i have 11 days left to cancel without fees), put an at&t sim card in my verizon iphone, and start a two year contract with at&t? Would I still be able to use my verizon iphone on at&t?

You just got your "unlocked" iphone5 with verizon (i would double check that) if you paid 199 for a 16 or 299 for 32gb or 399 for a 64gb… Those are not unlocked… Someone lied to you, the other thing is that you just signed a 2 year contract on that phone, so yeah you can cancel your service within 30 days of first signing up but they want their phone back! If you cancel and don't give the phone back you will get a fee of the full price of the phone on your final bill that you get from verizon. But if you decide to keep it and it IS unlocked, then yes you can use on AT&T

I think so.
I know if you buy it unlocked from apple it only works on GSM networks(AT&T, not verizon or sprint), but I think I saw somewhere that you can with the verizon phone. If you know someone who uses AT&T with an iphone 5, try putting their sim in it and see.

Yes, you can cancel the contract on Verizon and get a new contract on AT&T and put your Verizon iPhone on that contract. As they come unlocked, you won't have issues. But iPhone on Verizon is much better than on AT&T. I wouldn't recommend you to change the carrier.