What an ugly experience! This type of error happens when you don’t calculate your fee, especially when you are depositing from an option where the fee is also being covered from the same token you are sending out; the fee might be deducted from the amount you choose to send out.
I had such an experience before, but it was not in a casino. After a few arguments with the support, they manually funded my balance; you just have to follow them up without giving up.
You already did the only thing, that is to contact the support and they told you that the deposit amount was lesser than the minimum required so possibly you can't do anything further at this point. Consider it as lost forever and take it as a lesson to never repeat the same mistake ever while depositing funds on any centralized platform.
He did the right thing by contacting support, but we can’t be sure if the support attendant was a human agent or just some programmed bot. A human agent can’t reason with the customer in most cases and offer a solution, whereas the bot will keep on replying with what it was programmed to answer each time such a question is being asked.