Refused to cancel contract past expiry date

I have 3 contracts with Vodacom where the contracts have ended. I have called today to cancel all 3 contracts with Vodacom as I do not want to incur extra cost. There is currently amount due to them of R2709 which I will gladly make arrangement to pay off. Vodacom has now REFUSED TO CANCEL MY CONTRACT due to this AND THEY WILL CONTINUE ADDING MORE MONTHLY INSTALLMENTS TO THIS AS THEY CANNOT LOAD A CANCELLATION ON MY ACCOUNT DUE TO THE ARREAS AMOUNT. I asked to speak to a manager(TOELAPELA) as I have every right to cancel my contracts going forward in order to STOP ADDITIONAL ARREARS FROM INCURRING and they SAID NO! In this tough economic times when you are drowning in debt and really want to minimize expenditure and cost you have Mega Corporations like Vodacom continuously crippling average citizens with terms and conditions and loop holes to keep us indebted. I have been a loyal paying customer for more than 10years Vodacom (prepaid or contract) and this is manner in which you dismiss my concerns. I will take the food out of my 3 children mouths this month and try to pay you in full. You will be R2709 richer, but one loyal customer shorter. I am ashamed of you.