Refund pending for the longest time

I had a contract with Cell C and it was canceled but they kept on billing until I was handed over to their lawyers I settled the account with the lawyers but it did not reflect on credit bureaus. Since I was desperate and needed my home loan application to be processed I was advised to settle direct with Cell C , then request a refund. Until today my refund application is being escalated no other response is available from them .account over paid with R5000. How and where does one go for proper refund request