Shocking Service and Overcharge For Excess Baggage

My first and definitely last time I use this airline. I had endless problems booking in on line when I flew to Dubai in June 2019. I was quoted an excess baggage price and when I arrived at the airport in Cape Town I was charged twice the amount quoted. I had 8kgs excess baggage and was charged R1550. I was quoted by their customer service USD8 and was charged USD14 per kg. I should have paid around R800.00. I had to stand in LONG lines to try check in because I could not check in on line. I made 15 calls and sent 7 emails to the client service desk in Johannesburg. Emails were sent to Ratanang Molale and 10 emails which I have on file to Abera Mekdes the client manager in Cape Town. All this took place between the 23 June and 25 June 2019. I posted a complaint on their website and to date no one has even bothered to respond. HOW DID THIS AIRLINE WIN BEST AIRLINE IN AFRICA?????