It all depends on the provider ur with, when u buy an unlocked cellphone make sure it's compatible with your provider. The phones I have bought are only compatible with Rogers, AT&T and Telus(I think). If u don't know if it's compatible then ask the person selling it or if ur buying it from a store then ask if it would be possible to test your sim card with that phone to see if it's compatible.

I have a quick question. I have a very old i530 Nextel, it is several years old. I was wondering if I get an unlocked Motorola Razr V3i would the SIM card work in it? Like could I order the phone, then just switch out the SIM card and it will be the same?

Any advice would help. Thank you