Cancelation of mtn contract

I payed off my account from mtn cause I never get payed on the same day anymore yet every time I go into the shops to pay mtn still does a debit order middle of the month and every month is a issue now I need to cancel my account my self after I did that in the shop and been on the phone for over 2 hours and no answer GATVOL is not even a word best is they want to suspend my number again after I payed my account and payed my contract finally off aswell