OVERPAID ACCOUNT BY ERROR AND THEY REFUSE TO REFUND MY R8999.00 due to me!

I made the worst error last week and over paid for my WiFi acc by R8999 instead of R999.00 I spoke to agents via whatsapp and they said I would definitely get a refund. The next day, I was informed they can’t refund me I must speak to my bank. The reason being AfriHost no longer does refunds over R3000 due to ***** related activities. I spoke to FNB who said they can’t help me because it was an immediate payment therefor I must speak to AfriHost, they are even willing to help. Friday, a lady by Wendy Noble who is responsible for Accounts phoned me to narrate the above and even said they have been in touch with FNB and they can help if it’s a pay and clear. Fnb has denied this as their systems are not designed to recall immediate payments. Now I have been trying to get hold of Wendy again since friday she has not responded, she won’t take my calls nor return them. I have explained how important this money is and how I need it, she refuses to get back to me. I am at my wits end and would like to report this matter to higher authorities