How do I know if my phone is locked?

Your phone is likely locked if you have purchased it from a North American carrier such as AT&T, T-Mobile, or Rogers and have not previously unlocked it. Additionally you can install your RoamForce SIM Card into your phone and if a message appears saying "Enter Subsidy Code" / "Phone Restricted" / "Insert SIM" / "SIM not valid" or asks you to enter a code other than the PIN code, your phone is probably locked. Once your phone is unlocked it is unlocked forever and it will accept both your domestic carrier and RoamForce SIM Cards.