Safe-T claim confusion

I’m a new FBM seller, I just had my first return. When I entered the order number for the Sage-T claim the message, “seller needs to be debited to be eligible to file Safe-T claim “. So I issued the refund, went in later to file and the message , “not eligible because I issued a return . Only refunds issued by AmZ on behalf of seller are eligible for reimbursement. “ How do I get AMZ to issue a refund on my behalf?
My product cannot be resold if used, the buyer did use it used it with bodily fluids and it’s dirty The reason for return was not as described, then why did you use it . My product sells for $190 so that a big chunk of money to toss in the trash . What steps am I missing and how do I handle this going forward? Thanks in advance:)