The customer isn't always right, far from it.hey mate
since you work for GBT directly why cant you physically get involved and help this chap out? at least get him a new card, he spent a lot of cash for a product, and now he is getting the run around, Aorus is a new brand and you should jump at the chance to correct issues for your customers!! If I was manager then I know what I would do, the customer is ALWAYS right, because he paid for that right!
That aside, the other guy is a vendor rep. He isn't someone who works in returns, he just liaises with them. This is the guy doing his job, so let him do it.