Is not paying for services, like teaching about trading methods and PC's, bannable?

Hey.
A guy was new to trading and needed help and offered to give keys to anyone who could help him start trading. I added him from his reddit post, and he agreed to pay 4 keys after I could help him understand various aspects of trading. Since he was new to trading, I told him all I knew about Katowice sticker trading, did multiple pricechecks for him etc. He said his keys werent tradable yet, which I checked was true and said he will send me the amount when they are tradable. It has since been a month and he has traded his way upto a much expensive inventory and he's simply ignoring the fact that he has to pay me.

I dont mind not getting the keys, its a small amount of keys, what matters is the honesty and integrity of people. So I wanted to ask if this is a bannable action? or a SR caution marker? Or its just something that SR doesnt deal with?

Thanks for reading. Good day.