Srilankan Airlines — Active pnr boarding denial

Address:

SRI LANKAN <-CHANGI AIRPORT

I had a flight from Singapore to Mumbai via Colombo on 2nd oct, 20:10 pm. I had an active PNR but was still denied boarding even though I had reached the airport at 5:30 in the evening. At the check in counter I was in communication with two people, Shankar ( SRI LANKAN AIRLINES) and Krishnamala ( DNATA CSO). Both these people confused me all together and didn't issue boarding passes giving random reasons. At 7:30 pm I went to the ticketing counter and talked to Mr. Ming Chuan of Sri Lankan Airlines. He told me that my ticket was genuine and I should have been issued a boarding pass. The following are my flight details:
UL-309- SINGAPORE- COLOMBO
UL-141- COLOMBO- MUMBAI
PNR - 6RYRFO
I have been caused great loss to this and would like to aplly for a refund and compensation. There was a fourth person who was with us i.e Hemant Kachariya, who didnt have any problem travelling, but the three o[censored]s were denied boarding.