Bribery demand for Legal Heir Certificate

Hi everyone, I need some advice, and I’m pretty frustrated with this situation. My grandmother recently passed away, and we are in the process of getting the legal heir certificate. I’m the grandson, and my mom stays here with me, while her siblings live abroad and visit India a few times a year. When I went to the revenue officer to request the certificate, they asked me to pay ₹40,000 as a bribe just because we live in a wealthy neighborhood and my relatives are settled abroad. The officer's PA made the phone calls and said they could give me a "discount," bringing the bribe down to ₹30,000, but they were rude about it and insisted it was the only way to get the legal heir certificate. They even threatened that without the bribe, it would be impossible to get the document. We need this certificate to access insurance, transfer property, and get FD deposits from the bank, but I don't want to pay a bribe to get it done. I really didn’t appreciate how the officer and his PA spoke to me or my mother. I tried recording the conversation, but it wasn’t enough to take any action. I plan to record the next call and want to take this forward to the authorities. Does anyone know who I can reach out to for legal help or people dedicated to fighting these types of cases? I want these corrupt people out of the system! Any guidance would be greatly appreciated.