I have a complaint

I booked a flight on British Airways from Durban to Port Elizabeth. They say they close their gates at check-in 45 minutes before departure. So my flight time was 07:45 and I arrived at Check in at 07:00. The supervisor (Abigail Naidoo) says we are late. When we ask how can we be late when it's 07:00, she says the gate is closed. She then takes us to her manager who then called us *****, saying we are lying we did not arrive at 07:00. I asked her to check the cameras, she refused and said she's not gonna do that because she knows we're lying. She gave us options of flying the next day or rerouting the flight. We refused the offer because we were not late. She then decided to file for a refund which we will get in 6 weeks time. Then she asked Saps to remove us from the counters. So Tracy Beattie first call us *****, then refuses to help us or checking cameras to prove that we are late. On top of that she says we must be removed by the police or she'll lay a charge against us. It's a horrible experience and I'll NEVER EVER fly with British Airways again.