So i've seen quite a few ebay iphones with bad esn be it sprint or verizon. Now ive been looking around and reading many articles, but up till now i havent been able to clarify my situation. So i hope you guys can help me, because there are too many diverging opinions and too many differing explanations. I need something concrete and sure. Ok lets say theres an iphone 4 or 4s or 5 either verizon or sprint CDMA bad ESN or clean ESN. Ok so both normally have GSM sim capability "maybe iphone 4 doesn't". Doesnt matter if stolen, out of contract or lost. So its CDMA locked right, means that it doesnt use a GSM sim card and is only used on the carrier its locked to. But still retains GSM carrier sim useability properties. So here is the question:- 1. Can i use a GSM sim card of another carrier "Emtel Mauritius"? 2. If yes is there anything else i need to make it work, jailbreak etc? 3. Is there any limitations in itunes, does Itunes activate my sim etc, will itunes block the BAD ESN phone? 4. Is baseband freely upgradeable without any consequences? 5. If i get an Rsim7, can i use the Bad ESN phone on the go without trouble. Thanks for guidance. Please no assumptions and non experienced replies if possible. I wish to be 100% sure of what im doing.