You cannot be defrauded by something like this, unless you literally take their money and don't run them into whatever they paid for.
If you take payment, they expect you to down it while they're sitting outside. If you do, loot is theirs (unless you stated this price was for no loot, then that's another story).
However, in your case, if you specifically said "you need to pay after we run t10 for you for x amount of gil", then yes you can somewhat report it. Send a screenshot along with the report, because it's basically a service that someone is paying you for.
In the future, always demand money first politely. It's the best way.

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