Non Refund of Overpayment

I have overpaid my Sanlam Personal Loan on the 22/09/2020. I have since phoned them every 2nd day for my refund. To date I have received no joy after speaking to numerous consultants. When I ask to speak to someone in authority I am kept waiting for about 20 to 30 minutes before I am told that their seniors are in meetings and no one is available to assist me. When I want to leave leave my contact details for a senior person to return my calls. I am told that they do not return calls. I have emailed Sanlam all the requirements for my refund and I am told that they can not find my emails. I have the proof of all correspondence.