Malaka spice kp - Service charge taken compulsory

The min we were seated we told the waiter we would not like to pay the service charge as it’s not compulsory. But they said no you have to pay. And then one by one including their manager were coming and irritating us with same issue. We had our food with disturbed mind set spoiling our afternoon lunch. Later when they gave us the bill they had charged the service charge. I asked them to remove again same irritation from their side for not removing it. After ten mins they removed it and got the bill. Then the manger said sir what you did is not right as my salary will be cut for this amount you deducted. I mean what kind of management is this ? I paid them back the money but I am feeling as I m cheated and not got justice after spoiling my experience also. I really need to know how can they go against the government rules.