Resetting someone else's iphone
I have the iphone 6S of an ex colleague who returned his iphone to us but has kept the telephone number. I am concerned that if I reset the phone it may affect his current personal iphone too. I have the various log-ins and passwords for it and he is not currently using the icloud address etc that he used previously. Can I just go ahead or is there a different reset system I need to use? Many thanks - Paul