Had to pay R2100 for another flight for a 2 minutes miscommunication difference

My flight was at 16:20 on 26/01/2023 and I was at their desk before 15:00, even before they opened the check-in desk, so I had to wait for them to open. I checked in as soon as they opened and I was told that the gate to the flight will open at 16:00. I was not told at the time, as to what time it will close, but I was only shown later that it only opens for 5 minutes.

Because I was too early at the time, I took a drive in the Avis car, then I lost track of the time by very few minutes (less than five minutes). I got back at the boarding gate around 16:06 or so and I was told that I am late for my flight. I even laughed at the guy, thinking he was joking. But he was very serious.

But now my point of contention is that, even though I accept the fact that I was late, but I was only late by one or two minutes of the 15 minutes that the gates usually close. And also I was there in person earlier for check-in, to show that I am still going, and nobody tried to phone me to check why I am not around even though I just checked-in in person (Other airlines do phone, especially when it's only one person - like in this case). So, just for 2 minutes of being late, Cemair felt that I am not worth the trouble of finding out what was delaying me, and to at least make an informed decision as to why they have to leave me.