Vodacom online has bad service

Vodacom online has very poor service. I had a contract with them then I decided to cancel within 14 days because I couldn't upgrade instead I cancelled so that I can open new contract with them the phone was collect and credit has been passed but my name is still in arrears. I still get statements saying I owe them where else I don't owe them any thing I cancelled on April 19 and still now am still trying to clear my name because of their poor service.