Failed to give discount

On this mothers day I decide to go and buy me facial products and I see that there was a 20% discount allocated for the products. After checking my till slip there was no discount to the Eucerine Products. I returned to the store and they credited my account and they put the items through again but after I walked out I noticed they only too off R20 for each item and not the allocated 20%. Not only did I have to turn back but the store then closed. Now I had to wait for a refund. This is completely unacceptable and to make matters worse I had to run around and these people disappointed me twice and to make matters worse I now have to run around for products that should have been discounted only to be further disappointed and to think if I was ******** to believe they would do their jobs properly and not allow a loyal customer to walk without having received the discount. not only did they not check the items or the pricing they had neglected to promote the item to me as well. I feel very disappointed.