Clicks online bad service

Clicks online service has no regard for customer. They had a promotion for buy 1 aerial auto 2kg powder and get 1.1 L free liquid. I went to collect my order and only received 3 2kg autos without the 3x 1.1L. I lodge a complaint and received a call on the third day. Am told I cannot get the 3 liquids because the promotion has ended and that I should have added the 1.1L on my online. My order was placed during the promotion period and I didn't get any option that said I must add the free products. The consultant insist that option was provided when I ordered and that wasn't the case. The reason I purchased the items was for the promotion and still insist that they must own up to their promise. Why should I waste my time , petrol and money driving up and down to return the items at the store and still make followup calls for the refund?