Shocking - there is no customer service whatsoever

MTN - 1) Cancelled a data contract a year ago - Still being billed 2) Downgraded exiting contract in Dec - Still not actioned 3) MTN owe me money for the above and will not credit may account. Headed towards a Bad debt as I am not paying and they will list me on the credit bureaus. Lovely way to do business MTN. - Branch visits, calls to MTN 1 hour at a time - have wasted a lot of time trying to fix this