I want to use my one time refund but don’t know how.

I want to refund a knife I’ve used in game and upgraded. So I looked it up heard about a one time refund for one skin per account. But when I submit a request I always get a robot that tells me the same thing. I want to know where to go to use this one time refund or talk to a human. The picture attached is the message I have received for the last 3 tickets.