I'm having this problem too and I'm really starting to get irritated. At first it was when I updated my ios and it had an issue with Comcast. This took months to fix, then it worked for a couple months. Then a few days ago it was spotty and would only send pictures sometimes. Now it's not working at all and doing the same thing yours is. I know it isn't Comcast this time, because I've tried it on many providers. Snapchat works fine... Same with facetime and email. It's only imessage and honestly, I'm kind of furious because it was really convenient with a group project I'm working on. I was looking into an iphone, but if it's as unreliable as this is, there is no way in ****.