So basically I was sending iMessages (without any problems) to a friend of mine since we both had iPhones. My friend stops using the iphone but keeps the same phone number. My iphone refuses to accept that the number is no longer on an iphone and continues to only send imessages to it (unless I turn off iMessage entirely). I enjoy using imessage with other people, so I don't want to have to deactivate it. How can I get my phone to switch back to normal sms for certain numbers?