POOR SERVICE - FAILING TO TRACK CLIENT'S PAYMENT

During the lockdown my husband paid his Jet account using the banking details that THEY PROVIDED HIM WITH, so now they are failing to track the payment. They keep saying his account is outstanding even after he submitted proof of payment, they confirmed that the banking details are the same!!!!!!! SO NOW WHAT IS THE PROBLEM!!! i am really not happy with their poor service as this is getting LABORIOUS for my Disabled Husband, now he has to run up and down with Crutches for some payment he ALREADY paid!!! Can someone please help my Husband!!! and after this i will advice him to close this good for nothing Account!!!!!!