Spice Jet Airlines — bad behaviour of airport staff and not allowed to board the flight without any reason

Address:

Chhatrapati Shivaji International Airport BOM, Navpada, Vile Parle East, Vile Parle, Mumbai City, Maharashtra, 400099

Two of my relatives booked the ticket from Bhopal to Surat and they reached on time but the spicejet staff refused to board them saying we have closed the boarding and the flight took off at 6:30 pm where the scheduled time was 6:55 pm.
I want the airline to return my booking amount and also change the staff at the airport.
Screenshot of the ticket attached

Contact number: [protected]