Demand for a refund

I opened a contract with Mondo which was subject to certain conditions. Unfortunately they didn't meet those and instead of nullifying the contract, they opened a new line. I never activated that line but they charged me for contract I wasn't using. I phoned them questioning their behavior. They investigated the matter and ruled in my favour. Unfortunately they continued to charge me for the full term of 3 years plus additional month to month subscriptions. I have been phoning their office with no success. The number in question is ***. Kindly assist me to get my refund plus interest accumulated due to their negligence. Yours faithfully Mbokazi MA- ***.