Inconsistent service from rude staff at Mango Lanseria

I had a flight booked yesterday at Lanseria airport. I arrived at checkin 35 minutes before my flight and was informed that I missed the flight and had to go to ticket sales office, which I accepted. However, I then discovered that a travel agency messed up their flight bookings and those passengers were given our seats. The consultants were rude and very unhelpful at the tickets sales counter. I requested to be placed on stand by for the flight 5 hours later. Once again on my return, the staff at the ticket sales counter were very rude and uninterested. The checkin for the flight was closed for 10 minutes already, but they were not interested in assisting me. A family came in 15 minutes before the flight and were allowed to check in, so I was advised that the flight was then full. Please help me understand this inconsistency as I lost funds for car rental and accommodation. I now have to take flight at 17h25 today.

Very disappointed.