ABSA to FNB missing Payments

On the 16 April 2018 I made two seperate payments of R10 000.00 from my ABSA acc to his FNB acc to a customer for a car. The customer has since come back and said that no payments have come through. We have confirmed that FNB that there are no payments and nothing pending, it has been over a week and no one can help. I have been into ABSA and the keep calling online or missing payments, NO HELP. When i try calling they say money has left my account. I have confirmed account numbers and no issues there. Customer is threatening with legal action if this is not rectified. I must admit that this is worst banking experience i have ever had. I will be moving banks after this. There is always some issue with ABSA. I am not happy.