it is really necessary to give us more details. Bitsler has a pretty good reputation here, and online in general, so it is very difficult to conclude what happened here only after a few words from a completely anonymous person.
how much of your funds did you have in your account with them at the time of suspension? if you had something, can you withdraw it?
Except for VPN or multi-accounting, there are other things for which you can be suspended. Your country is not allowed, you cheat on their promotions, spam through trollbox etc...
any casino will not suspend players just like that, for no reason. players bring them profit.