Hi, guys I just got an iPhone 5 with at&t but I can't use the service till dec 7th because I'm taking over my sister line and that's when she get home. My question is that can I borrow my friends iPhone 5 sim that in service with at&t to active mine without harming either of our devices or line. Once I active it I will take the sim and give it back to him and use the iPhone 5 as a wifi device till the 7th. Then on the 7th I will put in my mini sim and take over my sister line. Will I run into any issues doing this?