Product dispute

The Glen - Shopping Centre We Put down R4000 layby on a Bosh dishwasher. Which was on Promotion for R5799.00 . When we went to pay the remaining balance and collect ,we were informed that the price that we were charged (price on display)was incorrect and that it was a mistake from the warehouse. They then told us we could take the display unit which we agreed too but once I asked if the machine will still have a warranty they changed the story and said they can no longer give us any machine as it was priced wrong. How is this right?? I have all the paper work as proof. You now have R4000 of ours and we remain without a machine that was promised to us.This is unacceptable!!! Will be going to hello Peter and all social media platforms.