Outstanding amount increasing instead of decreasin

I currently have a mobile contract that ends this year with MTN. I have not been using the SIM card for the past 3 months now. When I checked my statement for end of June and compared it to that of end of May, I realised that the amount outstanding is increasing instead of decreasing. Also, when I checked the invoices, the amount spent is also increasing. Mind you, I do not use the SIM card anymore, so the airtime goes unused every month. I have been attempting to call their customer care line for the past 3 days now and I give up everyday without talking to a consultant because I hold the line for approximately 15 minutes.<br> <br> This unacceptable and will never ever use MTN services again cause they suck!!!