Worst service ever. Shame on you

What a disgusting service from African bank.i called in last week Monday on the 22nd of July 2019 for my refund cuz I overpaid the settlement amount. I was asked to send a proof of payment which I did and days later nothing until I made the call only to be told that they never received any proof of payment. I sent it again but still nothing. A week later I sent African bank private twitter messages hoping to get any assistance but nothing. I'm very disappointed with the service and I don't think I'll ever wanna deal with African bank in future.