Unlinking Apple ID from a used iPhone
Hi
I've bought a used iPhone from one of my friends. It has his Apple ID, and I want to unlink it. Apple's tutorial suggests that I should reset the device, but I don't want to reset it. Is there a way to unlink the Apple ID, and use mine without reset/restore the iPhone? But also, making sure that my friend's email won't be required for iOS 7 activation in the future... Please advice
Thanks
iPhone 5, iOS 6.0.1