Srilankan Airlines — ticketing

I had the worst travel experience i ever had flying with most unprofessional third class airline called sri lankan... This stupid airline ruined my whole trip. Sri lankan was just connecting flight from cmb to sin bothways while all other airlines; china eastern, delta force and united airlines showed their professionallism and standards in aviation industry. My travel and tickets arranged by united nations environment program. On first date i was unable to check in since sri lankan said system not recognizing my ticket. Had to re schedule my travel following day only the change did was selecting china eastern instead of sri lankan. Everything were fine. But i missed the morning session where top people in the world talk about marine litter issue.
Again on return sri lankan did not let me board in singapore i missed the flight. I had to complaint to the singapore airport management that my own country national carrier is not letting me board while everyone alse in the ticket (China eastern, delta force and united) had no issue. They had to "force" sri lankan to issue me a boarding pass in next flight..
A country heavily depent on tourism need a professional carrier to boost national economy. But their professionalism can be seen in nature and number of costomer complaints in the web.
https://www.tripadvisor.com/ShowTopic-g1-i10702-k8050828-Sr…
http://consumerboard.org/com…/srilankan-airlines-complaints…

I am making a formal complainant to civil aviation authority. I gues sri lankan airline is still in victorian era while other airlines in 21st century. No more traveling with sri lankan.