MTN cancellation is a bitch.
Be prepared for many, many phonecalls, and about 5-6 hours, they hand you over to their "retentions" dept and then back to the original operator, 80% of the time you get cut off, then it all starts from scratch again, listening to pretty music, recorded bitching about all the call volumes (always the case) and trying to make you feel guilty about calling today, and then retentions trying to fix your stuff that they should have fixed 6 months ago.
Be firm, and be resolute.
Anyone who has made it through the whole MTN cancellation process deserves a T-shirt.