VERY DISAPPOINTED WITH FlySair

Very disappointed with FlySafair, its our preferred airlines that we book flights with a monthly basis. This morning my wife was flying to Durban and carried the hand luggage bag that she always uses on her trips. She was stopped at the gate and was informed that the bag was too big. I spoke to an attendant by the name of Trushna that refused to give me her surname, I informed her that its the bag we offed use has a hand luggage and we actually used a month ago when we went to Cape Town, she refused to hear me out and insisted we pay for the bag. If we had know that this was problem when we flew to Cape Town i would have checked the bag in. My point is, the very same bag was carried to Cape Town on the 3/06/24 with no issues, why was it an issue this morning?