Dead and still being billed 7 months later ......

My ****her passed away last year October and we cancelled his contract with MTN through one of the local offices here. We were informed that it was cancelled. Then he was billed. So we did it again AND went through the retentions division as well. Both times we were told that it was cancelled. Since then we have gone around and around from pillar to post with numerous calls and emails and visits to stores AND he still gets billed. Seriously! What do we have to do to have MTN stop billing us for a deceased person. I give up with this lot.