Not that it’ll do much good but I’d write a letter of formal complaint. Irrespective of the limit, the croupier indicated to the pit boss if the bet was ok. His acceptance of that, which would be on camera, should be binding. If you can afford it I’d get a friend to put the exact same bet on and see what happens. If they repeat the process then they are clearly in breach of their own rules accepting the bet. Extra interesting if you lose the bet and they take all your money.