iMessage is awesome except if you have moved to a non Apple phone and forgot to turn it off. In that instance some people have had trouble receiving normal SMS's from friends as iMessage was still trying to re route them.

Now I don't understand why anyone would want to leave the pretty world of Apple and it's amazing toys but I do accept that it happens and for them, Apple have launced a dedicated webpage to deregister your phone number from iMessage.

Off course you could just save yourself a lot of pain and heartache and upgrade to an iPhone 6!