Promotion not removed

Good day, yesterday the 24th June 2021 I saw an Alcatel tablet which was on display at Mr price Westgate mall for the price of R799. When I was about to pay, the guy who was helping me checked the price and now it's saying R1000. Now the guy is checking his messages and says the promotion ended on the 20th June 2021 which was 4 days ago. Cause now my child was happy that I'm buying him a tablet I paid R1000, but how is it my fault that the promotion was not removed on display cause I was interested on buying because I saw the price.