Your GSM cell phone is designed to be used with any service provider's SIM.
But the chances are that your service provider has locked your phone, restricting it and you to only use their service. But there is nothing to prevent your phone from being unlocked if you wish.

Your CDMA phone is also designed to he used on any cdma carrier (i.e. Verizon, Cricket, Sprint, etc). But the chances are that your service provider has locked your phone, restricting it and you to only use their service. But there is nothing to prevent your phone from being flashed if you wish. Most carriers now allow you to use any CDMA phone.

Currently Action Link Wireless can unlock or flash most cell phones! Contact us to confirm your phone’s compatibility.