Bad customer service

Checkers Pet Science. Had a special on the Monty and Me cat food 2 x 2kg for R99 i wanted 4 packs.

Came to the store, They were out of stock but said they would get stock on the Monday, Went the Monday again, Still no stock, Took contact deatils and saod they would contact when stock arrived.

The special ended last Sunday, and they didnt contact me. I queried it on Monday, and they told me, they did contact the people stating the supplier is out of stock, i told them but they didn't contact me. How can you run a special and say you would be getting stock, before making sure that your suppler would be able to give you stock.