MTN Billing

After being a loyal customer for many years the last 2 months i am in shock. I have 2 contracts with MTN with set limits on both of them specifically not to overspend. For the last 2 months my bills was incredabilly high. I phoned 808 and emaild the customer service line and not getting the answers i want. I asked them how is it possible to have spending when i have set limits their reply was because of a self service option thats being used. I have never used such function when asked for a itemised bill to see when how and where this service is used i want promised a itemised bill and still waiting and its now 5 weeks later and yet again at the end of April recieved a shocker of a account. When i recieved the first shocking bill and was notifed that its a self service option being used i asked them please to deactivate suh service cause im not using it and never asked for it and have a limit and how is it possible to have another high account when they have cancled the service or said they did and didnt. Something is not right and im not happy. Someone please advise.