App**** new Contract and then they pull out old ac

I app**** 1 February for a new cell phone contract with Vodacom. I know I have a clean Credit Record for more than 13 years. I was declined immediately stating ********** account!!! They said they will send it to a different department and escalate for someone to override the system. When I phoned this morning I was told that I need to speak to the Legal department. Legal department informed me that I have an old account to the value of R 11 000, but if I pay now I get 50% off. I did not even know I had an outstanding account with Vodacom, they cannot tell me what the phone number was which it was for. I asked when was the last payment made, they said 2007. I have not moved in the last 9 years, my ID number did not change in the last 9 years. I want this amount taken off my name. I do not acknowledge that it is my dept. I want it resolved and resolved NOW!!!