Overcharged on contract

I had taken out a contract 2 years ago with a Disney kids watch as an accessory. It never worked as per the technicians. Watch was returned. My account still being charged for the last 2 years. Contacted the store in Westwood and pavilion. No assistance from management. Even contacted vodacom directly for assistance. Still no reversal of charges but rather continuance of charge for something I don't have! Pathetic service.