A very unpleasant situation, which is another reminder that you should always read the user agreement before using any gambling site.
In my opinion, the gambling site should have programmatically made it impossible to bet from the bonus account on the listed games and introduced the necessary limits. Otherwise it all looks very much like a not entirely honest business, with its creators covering their actions with a user agreement.
We should also understand that these gambling platforms are out for profits and nothing will give out profit "if" there are no traps set for those who can't read platforms TOS. Something like this happened to me some years back with some online courier company, after placing my orders with the best deal, i forget to read about their agreement and when the time of delivering came they sent me some messages that my country wasn't among the country for such deals, then, return my funds and my account was suspended till-date.