Unacceptable flight delay

I am so disappointed by the delayed flight that I had to just accept on flight MN454 from Cape Town Airport to Lanseria. Why would I be sold a ticket for a particular flight time and have it delayed by about 2 hours for no apparent reason. I received an sms to tell me about the delay, and when I called the call centre to find out if anything can be done for us to get an alternative flight, I was told that I just need to accept it. And then when the delayed time arrives, we are told that the aircraft is even further delayed. This is not professional at all from an airline that keeps singing it's own praises in media adverts.