Useless service

We have a business account with MTN, with 5 different numbers being on the account, ever since our latest upgrade almost 20 months back our bills have increased from around 3000 per month to 12000 per month and MTN's justification is that this is due to data charges, nevertheless we decided that we wanted to proceed and cancel services with MTN, pay the cost, and move to another provider, back in july last year, and after multiple calls some lasting longer than an hour, I was directed to the credit department (Cathy Botha) who emailed me a cost that needed to be paid and forms to be completed to effect cancellation, I completed those forms and requested that a debit be done of our business account for the monies and assumed that due to the bill being on a monthly basis it would be done at month end, nevertheless this was not done and after numerous calls once again to the call centre I was put onto another guy from a different department who would assist, this guy sent me a cost breakdown which was roughly 5k more than the previous one, seven months ago, I've queried this via e-mail and till date I have not received a response, however we continue to be ***** with bills timeously.