It's always complicated with bonuses if you don't more detailed feedback from the casino. If they say you violated bonus terms, it could be many different things. You could place a bet over the max. allowed bet size, you could play restricted games, you could delay game rounds (you play a game with bonus money until you get into some bonus feature or free spins and then you close the game), they may found out you have multiple accounts and the other account already used bonuses...
Anyway, I believe the casino should always inform you what you did wrong so you have a chance to defend yourself. Try to contact them via all possible contact methods (the VIP manager might be on vacation, changed his role / job etc). I can see you already submitted a complaint, but I think it's worth to contact them via all possible methods. If they don't get back to you within 2 weeks, then I'd complain as well.
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