MTN mystery charges

Since October 2025 my phone keeps being suspended due to a mystery amount of over R4000 added to my bill. After many calls to the service centre I am told each time that an arrangement is in place where I pay my normal call and data costs and MTN will come back to me with an accurate description of what the charge relates to. Each reference number is apparently escalated and then on the next call am told it was closed with no resolution. I feel that as the company invoicing me they should be able to either inform me as to what the invoice item is or else remove it from my account. Instead all that has happened is they re-open the line for a few weeks and then suspend it again without trying to resolve the issue. I have had the number concerned since cell phones were launched in South Africa and feel that as one of their longest paying accounts a little service in return for the many thousands spent with them would be the least they could offer. Highly disappointed!