I think the best way to start dealing with this scammers is withholding their coins even after they made correct payment until after a long time and pretending you didn't notice they made payment and filing an appeal against them. They do all these intentionally.
Doing this might have a few negative impact on your account.thats why the best way I believe to handle this situation is giving them the worst review, there's a kind of review you'll give a trader, it'll be difficult for them to trade easily on the app, and that way you'll also be creating awareness to others too, especially those who usually take out time to go through the profiles of buyers before initiating any sort of transaction with them, and if they bump into such review, they'll just have to skip them for another person.