Indian Railways — railway police asking for bribery

I am travelling in sampoo kranti superfast express train number 12393. Date of bording 07/june/2018. I got genral ticket and had paid fine for sleeper class in patna before boaring the train. I found a vacant seat no. 7 in s3 and i sat there.in s3 two police men came in mughalsarai jn and asked me to pay bribery of rs500/- for sitting in that coach. When i denyed then they send another fellow who has paid him rs200/-. I left the seat and later on i sat there with the permission of that seat owner.in kanpur central the two police men came and on finding me sitting, they pulled me with my collar and started beadting me. They told that they would throw me out of moving train if i sit without paying them. Pleas help me.