Hello. I bought this used iphone 4 from friend with ios 5.1.1 and baseband 04.12.02, jailbroken with Cydia. This guy used it with Vodafone carrier (Spain) it always worked well, but now I want to use it with another carrier, and the phone seems to be locked. Didin't had a chance yet to try again with his SIM to check if it's a general problem or just mine. On the phone display in the upper corner it's switching from "serching..." to "no service" and so on. What can I do?