Vinted complaint: Missing Refund

Bought an item from a seller on Vinted and cancelled the order the same day. The refund was sent but never arrived at my bank account. I have contacted Vinted regarding this over a dozen times only for them to produce the same copy and paste answer almost every time. They claim it is an issue I need to take up with my bank which I did but as the funds never reached the account in the first place there is literally nothing they can do and in their opinion it is down to vinted to recall the refund and re-issue it to me. I have relayed this to Vinted numerous times but they refuse to listen. One agent I spoke to said if I can send them a copy of my bank statement showing that the payment was made but the refund never arrived then they can do something about it, I did this and they saw that I had not received the money and then immediately reverted back to telling me that I need to speak to my bank as there is nothing they can do about it.