Indigo airlines didn't let me check in .

I had a flight from Istanbul to chennai at 8 : 15 pm . I was at the check in counter at 6 :55 pm . They say they close check in 75 minutes before departure but it was closed even earlier. The groundstaff didn't help me check in and was rude and there was no indigo airline office at istanbul airport. I was stranded for one whole day all fatigued and booked a different flight back home the next day . I mailed them regarding this and they are saying i reached check it counter after 75 minutes. I asked them to check cctv and they refused . Please advice on how I could get help regards this legally , this has caused me so much distress . Also on their e-ticket pdf baggage drop time was written as 7 :15 pm .