Dear Friend,

You are entitled for 21days from your basic salary,
Apart from that company cannot terminate you by just verbaly, they should issue you a termination letter.
suppose if your company refused to give you the gratuity, you don't have any prove to say to the court that you have been terminated. and you cannot make any actions against them.

Basically a company can refuse to give you the gratuity if you have caused anything against the company policy which will be a lost for the company.

Anyhow fight for your right mate!!!

Good luck,