Angry client

I am soooo ****ed with Ackermans not the pavilion manager having a smirk while addressing my issue and not taking it serious what disrespect yhooo, they was a promotion that buy items for R600 and you get R150 off and that's exactly what I did to my disappointment the shoes didn't fit my son and I went there the next day I was told they out of stock and they don't have and I went again a week after and no stock and then they had stock and I was told that I have to pay extra I have forfeited my discount to my surprise how? Why am I getting penalized for the store not having stock? Ackermans this can't be the way you treat clients impossible I am ****ed