[iCeDmAn]

Like the title states, I currently own a locked iPhone 3G on the ATT network. The problem is I am moving to Poland for medical school at the end of the month and will need to get a new phone over there. I would love to keep using my 3G and am aware that some carriers provide it. Would I have to unlock my phone to use it on their network or can I just swap out the sims. TIA!!!

[sziklassy]

You will need to unlock the phone. It is locked to ONLY the provider you bought it for. In your case you can only use it on the ATT network in the US. And grats on getting into med-school! I am currently in Vet School myself
Good Luck with your phone!