Can a batter be deceptive?

This weekend at my baseball game, I got up to bat with men on 1st and 2nd base, and I called time before the pitcher started his windup. The ump didn't give it to me, and the pitcher stopped in mid-stride going to the plate. The umps called it a bawk, and the runners were given 2nd and 3rd. The coach on the other team went on to say that the batter was being deceptive, and it shouldn't be a bawk. Is this true or what is the real rule?