I don't know how to address the issue. But FortuneJack is a reputable betting site, they will have some reasonable explanation of this issue. Were you able to bet more than $280 on sports betting in a single bet before receiving the cashback bonus? I think their representative has missed to read your post in their ANN thread. You should send them a PM with the link of this thread.

BTW, as CryptSafe has said above. You have to provide some evidence here, as an example: the screenshot of your account bonus page.