Over charged and no service

I took an Mtn router contract of R320 per month. I missed a few installment this year now am owing the R5200. Last month i called for payment arrangements i was owing R3700 . I letf money in my account i was not debted. Today am owing R5200. I have been calling to cancel the contract thy will transfer my call to collections n it will never be answered router number ***. Contact number ***