Customer service bad

Very disappointed with dischem's customer service, i do all my shopping with you every month. this last month i spend R3500 there i went to the branch at the pearls in umhlanga, i bought the 2+1 deal usn but didn't realize i had taken a biogen product instead of USN, i called the store and spoke to a lady by the name if Nikita she told me they are unable to help, i then called the la Lucia branch as i always shop there and it was the first time shopping at the Pearls, Nelly assisted me, she was kind and tried to help me however the manager advised i'm unable to swop out as the sale is over.

Very disappointing that I'm always spending every month to find that Dischem doesn't care about the customers.