Cancelled Contract in JAnuary now you handing me over to debt collectors

Hi my contract had expired with Vodacom and I was on month to month. I ran into financial difficulties and then cancelled my month to month contract in January 2017. You continued to bill me up until who knows when and you claim I now owe you over R9000 firstly I don't have this money, secondly I cancelled my month to month contract with you guys and thirdly my service was suspended. I need this sorted out and these shark you call debt collectors to please stop calling me because I don't owe VODACOM any money.