Will my iphone 5 work in Peru?

I'm currently in Peru. And my iphone5 that i had a plan with tmobile (prepaid) in the US changed its service to Mobistar but i can only receive messages and i can't do anything else. No internet or phone calls. Is there any way that i can change it so that i can call into and text into the states?

Added (1). My phone is unlocked

Unless your phone is unlocked. Then it should be fine. In the US The reason why phones are so cheap is because they are locked to the cellphone company, so you can't use it anywhere else except the company u r using it in. If you bought your phone somewhere else and is it at least $500 USD, then it should be unlocked. If your phone is unlocked, then you can get it unlocked at Verizon (i heard that it was free).

Actually if your 2 year contract is up you should call your carrier and tell them to unlock it.

If your phone is unlocked and you have a Movistar SIM card from Peru (and a Peruvian phone #), it may be that you just need to buy airtime. If it is not a Peruvian SIM card you may have to buy one.