Bad service

i went to Jumbo in Sebokeng Thabong shopping mall, to buy a dress during christmas for a celebration, it was late in the afternoon i was leaving for joburg, i got a dress and lybe a few items, the dress scanned 0.00, i was told i cant have the dress, its not for sale, i needed the dress so bad, the cashier and supervisor on duty told me they can't help me, i was so dissaponted and hurt, as i needed it for the celebration that evening. My question is why was the dress on the sakes floor if it was not for sale. I wrote an email to their head office that was never respondinded up to date.