Flight leaves 30min early and without me

I was scheduled to fly to George from Johannesburg on CemAir flight 5Z0124. The flight was scheduled to depart at 2:30pm on the second of January 2019. When I arrived at the gate to board at 2:05 they informed me that the flight had already departed. They said that they couldn't contact me because I booked through a website so they just left without me... Half an hour before the scheduled time!? This is unreal and unacceptable. It was the last flight departing to George airport for the day and as I came from Hoedspruit that morning I was stranded in jhb. The people at the CemAir bookings counter refunded my money for the ticket but did not compensate me for the inconvenience of being stranded in Johannesburg. Most importantly they could not refund the time I could have spent with my mother on her birthday or the time I could have spent with my family who went back to China the next day. What ever money CemAir saved by leaving without me I truly hope was worth it because the value of what I lost is immeasurable. I work at a lodge in the Kruger National Park and we send easily 400 people through CemAir a year. I will no longer be able to recommended this airline as an option and will be obligated to warn my clients against this inconsiderate and self serving company.