SIM card is too small for my iPhone?

So I just I got a new iPhone and I tried cutting my SIM card but I ended cutting it wrong and my iPhone can't read it. Can I get a new SIM card? My provider is AT&T

CALL your PROVIDER

I don't see why not. Contact AT&T.

Go to a store that sells phones (and plans) for the carrier you are with and ask for your service to be transfered to a new sim card. Either state the size you want (nano for the 5, micro for the 4 &4S) or tell them which model you have. They can call tech support on your behalf and organise the activation, or you can do it yourself.