Flight price error

I logged onto your website this morning to book a flight from Cape Town to Johannesburg, The flight time was 16:30 - 18:30 and it was R805 and I selected the bag option. The price went up to R890 total. I filled in all my details till the payment side which when I was clicking on it, it pops an error message. Now I've tried logging in again and it shows a different price which now is R935. I need clarity on this ridiculous price increase of less than 5 minutes.