IPhone – My number is associated with iMessage on other phone, how to remove it

iphonemessages

Good day everyone. For only 1 hour (!) I used my relatives iPhone with my sim card and that's it, he keeps receiving all of my iMessages. I tried checking in iTunes all devices associated with my account and his device is not listed. I tried to log in and log out to/from iMessage on his phone with his apple ID, still won't help. How can I stop this nightmare!?
When I go to iMessage settings>Send & Receive on his device, there is only my phone number listed, how do I remove it without smashing phone to the wall?!
Thanks and have a great day

EDIT. After talking to apple support for some time, they removed my phone number from my friend's iMessage. So I guess if you are facing same problem you have to contact support.

Best Answer

Following the instructions on Apple's Deregister iMessage should help you resolve this issue.