I've seen conflicting reports on this and I'm not sure what is correct. I have a Sprint iPhone 4s (no longer active with Sprint) and am hoping to use it in Belgium. Sprint has given us a master security code that they say other carriers can use to activate the phone for their networks. Apple lists this model number (A1387) as either GSM or CDMA. I haven't seen any clear guidance on this and I'm wondering if anyone has first hand experience with this phone model.