Suspicious Charges and No Investigation

On November 27, I phoned MTN regarding mysterious charges that appeared on my bill. After an hour on the phone and discussion with her supervisor, the customer care consultant Valencia was unable to tell me what they were for. She promised me an investigation would take place and I'd get feedback within 5 working days (first ***). Two weeks later, I phoned again, waited for half an hour and phone call was dropped. I decided to email. The response was: phone the call centre. I did so again and the consultant said Valencia would phone me back with feedbacl (second ***). I've never received a call. Now when I email customer care, they ignore my requests and the charges have gone off my account. My contract is up for renewal in the next month or two and I'm certainly on the search for a new service provider since MTN obviously doesn't value my business.