Charge for carry on?!

I am livid. I specifically paid extra to ensure that I can take my guitar on as carry on. Their website only specifies that carry on must be under 7kg. Even though this was true in my case, I had to pay R410 extra because the dimensions of the guitar were too big. Supervisor Marina Schuster was of no help and in fact was rude when I explained that I had already paid extra. Never flying with kulula again. You might as well pay more and receive quality service. No other local airline has ever had this problem with my guitar.