Poor service

Oral b pro expert advertised Buy any3 and get the cheapest 1free.THE add is a copy cat of promotions at clicks.At the till points the cashier indicated it was not on promotion and wanted to know we're. I had seen the advert,the supervisor was called(name unknown) she immediately pointed out the page numbers with the 3 for 2 specials ? That was not my query then she said I had the Incorrect product she has to check with management .she arrived back saying the manger said that they are out of stock?????? The correct product was at the till point with me!!!!!ALARM bells does management In this store know their product/promotion?I contacted customer services who in return called the store, with NO response from management I has a customer Went To pick n pay with the intention to purchase an advised product Which clearly states Buy ANY 3 and get the cheapest 1free .ANY is the key word.Senior management could off turned this experience around by a simply appearance at the till point or a telephone call which never. Shame on you no customer service. Retrain yourself on service excellence,promotions before execution