IMessage, Facetime not working
I have an Iphone 4s and my friend has an Iphone 4 and we are trying to FaceTime and it's not working. This has nothing to do with wifi it specifically states that the other person doesn't have FaceTime. In our contacts we have eachothers' numbers listed as Iphones. I have no clue what is going on, or why it's not working. My only conclusion is that it's because I have a 4s and he has a 4. Please help.
iPhone 4S, iOS 6.1.3