Refund for a busy cafe?

I work at a store in the middle of a busy plaza so it’s very usual, especially when the weather is nice, for the café to be filled. We also have this regular, who has been frequenting our location for years now, who likes to sit in cafe every order. Recently however, he’s been requesting refunds on his drink (venti americano) every time cafe is full and he can’t find a seat. There was even an instance where he harrased the cash to get him a chair from the back room because he “know we have them back there”. He has no physical disabilities that we know of, and has never communicated that he needed a seat for health reasons. But everytime the cafe is full he says that he deserves a refund because “sitting is a part of the experience”. And without the seat he’s not getting the “full experience”. It’s a complicated situation because he tips big and is extremely nice until he has no chair. This has been going on for months now, anything we can do/report to?

TLDR: Regular able-bodied customer demands refund ever time he has no chair to sit in.

Edit bcs ppl were asking: he orders in cafe. never mobiles