friends iPhone isn't receiving my texts and calls

befor the problem started i could text and call my friend without a problem, but now when i text him he doesnt get thim (i know its not a delay cause thy never come through) or my phone calls. so i called my carrier and they said the texts and calls have been comeing through there servers and are sent.

iv tryed restoring my phone and all the other things other sites have siad to do, when i start a chat with him it comes up as imessage like normal and i type the message and when i hit send and it siads it sends but the little delivery thing that appers at the bottom never comes up but it. but i cant text everyone els that imessage or just text they all get them so it seems its just him

pleas help

best regaurds Keith

i have and iphone 4 16gb