MTN Service

After making payments diligently...i receive a message informing me my line is suspended as my account is in arrears. After making contact with MTN i am advised that i have an amoungt oustanding even though i have made payment. It seems my monthly contribution has gone up by almost R400 with no explanation. I have not added any services or made any upgrades in the last two months. I then get sent a bill with an early termination charge?! What is happening!!

I have been with MTN for 14 years - I really need an explanation!