Worst service provider ever🤮😡😠

I am so disappointed in this service provider the level of service that my mum got is by far the poorest of them all.... My mum had a contract under Cellc for many year until last year October when she decided that she will no longer upgrade I her daughter have been paying the service provider on her behalf so we the contract was canceled I had mistakenly made payment on a closed account we have been inquiring for a refund since they had said the process takes 10 working day till today we still struggling to get a refund even though we submitted all the required documents her ID copy and my bank statement that shows that I made payment on the account as proof.... Still no refund to this day or even a call to update us as to how far our case is