Denied special no stock wrong price

Spar currently have a special on Doritos s chips for 10.99 a pack ,on the shelve they had a special price signage advertising the special price of 10.99 , they had two shelves of the deritos and the the only price point in sight was that of special price (I have photos as proof ) . I get to the till to be told the special is for 150g not the 250g pack I had , I explained to the till lady that her price point was therefor incorrect and that I'm not prepared to accept this , she made mention this same situation occurred a day earlier as well , so clearly this was a complaint that was not dealt with when it first occurred which is bad enough , another staff member came to the scene I took him to the run showing him that there were two shelves fill with the 250gram party pack and the only price point in site was the special price I said irrespective on the signage saying 150 gram it should not be placed as the only price point applicable to the two rows filled with 250g , the 150g was in fact sold out which is even worse given it was advertised , they had left the special price even though they knew they had sold out and then we're prepared to give the price its unacceptable practice