REFUSED TO BE GIVEN A PRODUCT ON A MARKED PRICE

I visited the store on the 21st February to buy a sport bag. Realising that they had a fewer selection, i noticed the was bag a size i was looking for in the window display. I called on the assistant who I later heard was Miss August and requested her to hand me the same bag from the shelf as i was already on the tills to pay. I asked her the price and she said it was 199.00. She handed the bag to the cashier and I requested to them to change the one I was buying with the new one. I noticed that the amount i was to pay was more as the bag was priced 199.00 reduced from 199. She took the bag out of the pack and scanned it and it amounted to 399.00. She called the manager who retorted that the price could have fallen from other items. I questioned him and found that was an unfair practise as i exchanged the bag i was to pay because the assistant gave me a cheaper one. The manager pointed that it was a mistake. i refused this as the mistake was on their side. All bags were in plastic bags and had the price tags outside.<br> <br> Please tell whats my right on this. I refused to take the bag on a new price.