I sent my headphones off to be repaired. They never repaid me the whole fee

I sent my headphones off to be repaired a month ago as the sound was only playing out of one ear. I got confirmation that they had received my old pair yet never repaid me the £29.00 hold fee I had to pay. I have screenshots of the conversation with Support who said I would receive this money. Not too sure what to do.

[Re-Titled by Moderator]