They blamed me for a bug in their website. Absolutely terrible customer service

I was booking a flight home to New Zealand I selected the 23rd as a the date and assumed that that was enough to get the flight on the 23rd but I didn't realize they had booked me for the 13th. I thought maybe I was in the wrong and messed up somehow so I tried to change the flight after paying they then tried to charge me R20000 to change the flight but despite the fact I verified that I had chosen the 23rd multiple times the amended flight was going to again be on the 13th. support was completely unreachable during their operating hours and when I finally got through to them on the 13th they blamed me. Disgusting