Cell C are ******

My mom had a contract for which i was paying. In May 2023 i paid the remaining balance, only to find that it was overpaid with 960.00. We contacted cell c and they promised to refund the money. We submitted every document they asked for until today they still have not paid and they don't even reapond to emails. Am thinking of going to Ombudsman... They are ******. I want my money back!!