Company denying my earned leave balance payout after resignation, what are my rights?

I resigned from my job in Bangalore after 5 years of service, and I had 30 days of earned leave balance. According to our HR policy, this should be encashed. But the company is refusing to payout, saying there's a new internal policy change. This was not communicated earlier and wasn't in my contract. I feel cheated and need the money urgently. What legal steps can I take to recover my dues?