Mango Airline - UNREASONABLE

I cannot describe how dissapointed I was with Mango airline this morning. I was 5 minutes late for the start of boarding time and they wouldn't let me on the flight. When I explained to them that this was the first time I had been to OR Tambo and I had trouble sorting out my car rental they paid little attention. I understand that they have measures in place for late coming, however I strongly feel that they can make exceptions for cases when the passenger was only 5 minutes late! The service I received was incredibly dissapointing. I do not foresee myself supporting such an unreasonable airline!