This is the notorious Grand prive group. They sent me a coaster for my coffee cup last year through the post.
They often pull stunts that can be viewed as predatory or rogue, just ask the affiliate community.
I played for a while when they were Microgaming and decided to target the UK after banning UK players for some time. Early on, I saw an advert for a scoreboard slots wagering tournament that never happened, and after one decent win, and shortly after I had a phonecall from them that suggested I was being viewed as potential "VIP Material", I suddenly started encountering errors with their promotional interface. Live chat said it was merely a technical problem and there was no question of me not being eligible, but they were lying. They had given me a bonus ban within days of that phonecall from their host, but bodged it so that I still got the offers by email and in the lobby. I quit playing there and then.
Some time later, they offered me a free chip. After I took it, they contacted me and offered another deposit bonus. After I took that, it was another chat with a host where all sorts of promises were made, and I told them that because of what happened last time, they would have to work hard to win my trust. Yet AGAIN they tried to trick me, as after making the agreed deposit (and losing it all), the promised regular offers never came, and again I eventually uninstalled the casino.
Next thing I hear is the row about the overnight flit from Microgaming to something I had never heard of before, shortly followed by the row with affiliates where they lied that all 5 casinos were closing for good, and hence no more revenue would be generated for affiliates. Whilst telling affiliates one thing, players were getting a different story, being asked to sign up at new casino (the motive being to bypass affiliates). When another player started a thread about this, they were told to remove it as the existence of this new casino was supposed to be a secret (they didn't want affiliates finding out obviously).
Now, years later, they are still up to the same tricks, but many players are not aware of their shady past, and so end up getting shafted.
By all means fight hard for the remaining balance, but learn the lesson and steer clear of Grand prive properties, including the ones they pretend are nothing to do with the group (Big Dollar, Villa Fortuna etc - if they are still around).