Vodacom - No help (bad service)

I had a contract with Vodacom , that was suppose to be cancelled in 2013. Now when I try to take out a new contract, I was declined due to the fact that Vodacom never cancelled my contract and now telling that I owe them R4300. I've been on the line with the legal department, and went instore and tried all from my side but seem this cant be solved. The only feedback from them is to pay the outstanding dept. BUT THIS IS NOT MY FAULT as Vodacom never cancelled this contract. Any advise?