Account closed after placing one (losing) bet???

I create a bet365 account on December 2nd and place a very reasonable (+575) $10 bet on the Broncos vs Browns game. The bet loses. As part of the promo that bet365 was offering at the time I signed up, I received $150 in bonus bets for depositing and playing my own $10.

I open the app today, December 5th, and am met with a notification that my account is restricted. I send an email to inquire about this restriction and the response I get is that "they no longer wish to accept my business" and that they will be closing my account immediately.

How is this something they are able to do and get away with? I deposit and play my own money, they give me bonus bets, then close my account before l'm able to use them???