iMessage only working for some contacts
I have never had problems with iMessage before. My friend had an iPhone and he just got a new Droid phone. With iMessage on, if I text him, the texts only go to his old iPhone and not his new Droid. I have to turn iMessage off to get my messages to go to his new phone. If I turn iMessage off, I don't get iMessages on my iPhone. They only show up on my iPad as iMessages and don't show up on my iPhone at all. How can I fix this?
iPhone 5s, iOS 7.0.2