Poor service delivery

I went to the Travel Expo on 10th February. Wanted to book a multi city flight ticket. Was quoted R17,609 which was apparently also including a discount. When I went onto the flight booking sites to have a look at the comparison, found the same routing and flights for R2000 cheaper. Flight centre advertise as offering the cheapest flights guaranteed? This does not seem to be the case, I would have thought that they had better access to good prices as the are in the industry. Really disappointed with this costly mistake.