How do you change your cell phone number on the iPhone?

My aunt just got a phone from my uncle, but it%26#039;s his number, and they have different phones so she want%26#039;s to change the number... I don%26#039;t know how to and she wants me to do it.. help?|||You cant do it by yourself or from the device. You have to call your service provider(which I think is AT%26amp;T) and they will change it free of charge.|||put ur uncles sim in the phone and use itunes to activate it to is number there is a release button to take the sim out ull need a pin|||sim card underneath the battery. just switch em out