A-Z customer sent back different item buyer refunded

Hi all,

A-z was opened got a message stating we had 72 hours to respond, we got all the information together and before we could submit it (about 12 hours later) buyer was refunded and a to z found in their favour.

we uploaded the images showing different item returned with different serial number, the appeal was denied, have contacted the managing director and we get no response other than to message if no reply in two business days.

Anyone able to advise.

Thank you