I have claimed for a refund of R****ecause I had to pay for my orthopaedics appointment

I have claimed for a refund of R****ecause I had to pay for my orthopaedics appointment. I sent them the receipt also stated on the email giving them my banking details. They process the claim only to find out two weeks later they sent it to an bank account I closed years ago. When I was on a call with one of their agents mid conversation she hung up on me and didn’t even bother returning my call. What is the point of writing emails to them if they don’t read them they just proceed however they like. They then tell me I must take it up with the bank they sent it to. Who gave them the right to pay to that account. I want my money