MTN is trash and is horrible at customer service

In have a contract with mtn on behalf of my mother. I pay R133 on this contract, and for the month of July and August I was billed R276.76 and R520.31 respectively. I then enquired on August the 16th and they told me it's recurring data that someone activated on the phone, mind you my mother stays alone and knows nothing about technology, the only thing she knows is to make and receive calls on that phone. I then ask the mtn agent to cancel this, and she gave me a reference number and said it will be resolved in a maximum of 48 hours. then this morning I see a notification that mtn billed me R232.05 for the month of september, and I call mtn and give them the ref number I was given last time and the agent tells me there is no response on that ticket, no response? a month later? like what the hell? mtn now owes me R630 for over charging for the last 3 months. to say I am ****ed is an understatement. They just lost me as a customer, mtn is trash