WORST SERVICE EVER!!!!!

Cell C is the worst service provider. I have cancelled Cell C +- three years ago. Ever since they still provide me monthly statements showing that there is still a credit due to me. I have been requesting a refund for the past two years and to date nothing has been forthcoming. To date they have now confirmed the amount due to me but still request that i prove the amount by providing proof of payment. I am at my wits end but i will never recommend anyone to make use of the services of Cell C