Ackermans bad service

I have n account with ackermans my name is antonette Mali I have never missed any payments with them instead I pay n extra every month ...I have received emails n sms that I'm listed as default I submitted all proof of payments to them n they have not updated or called me to give status ...every day I have ro call them n stay long on calls with my airtime they have no decency to call me n acknowledge that it's their system error ...today 8 days later I'm still getting messages that I owe yet they admitted that it was system I am very angry n I want to close the account I don't how to go about it