Substandard and LATE!

My fiance was to board a mango flight from King Shaka to Cape town on Tuesday afternoon, only to be told that the flight was rescheduled, without notice or communication. She was sent to fly with Safair. I am not happy about this at all, as the quality of Safair is terrible. We paid for her to fly with Mango for a reason. Not to be downgraded to substandard cabin conditions and more than an hour delayed. This is completely unacceptable from Mango. We paid for something specific and received substandard value for what we paid. I need to understand why we needed to settle for this. I understand the there are pilot strikes, but surely we are entitled to receive what we paid for.