A friend of mine owns an iPhone 4. He was from carrier X and recently cancelled that contract and got a new line from carrier Y. Problem is the iPhone is locked to the previous carrier and they ask for 260 in order to unlock it. I've checked myimeiunlocked but there's no option for that carrier (We're from Spain). So, my question is: Can I jailbreak this iPhone 4 even if it's on 6.1.3? And if so, what do I gotta do in order to let him use another carrier once it's jailbroken? Thank you very much.