No CAP after requesting the account to be capped

I signed a new contract with MTN when I purchased a new cell phone for my son. After specifically requesting to cap the account at the monthly premium I still received excessive bills so phoned the call centre on the 8th September to ensure that the bill is capped and that the data supp**** is the only Data that will be allowed. Despite them confirming that this had been capped I received a Bill for R 1588 this month. I am the customer, I requested that the account gets capped and yet MTN allow the bill to be run up!!! i have been a loyal MTN user since 1995 and have three contacts. I will not be renewing my contract with MTN because they are not there to please the customer. The cell phone number for this complaint is ***.