False adverti*****t, refusal to process refund and appalling service by online mediums of communication

I am writing this review as I am extremely dissatisfied with how the online channels of communication have handled my query (Facebook messenger and live chat)

I made a purchase online where 2 items did not scan a promotion, I initially queried the promotion (via FB messenger) prior to making payment where I was advised to proceed with purchase then provide an order no. ( I was clear on which items I wanted and which promo I was quering) and a refund on the difference will be processed. I did as I was advised only to be told that I made a purchase on products that where no longer on promotion, the promo was for the previous month (I was told this via chat) mind you I'm making my purchase a good 3 weeks into a new month! Furthermore the promotion was still visible online at the time of me quering the refund and this was the response I received - " Hi *my name* , This is an error and we will ensure it is removed." ( This after I sent screenshots of the product still visibly showing the promo and the date 24/07/19). Am I wrong for wanting an item at the price that I saw? Furthermore I was clear on the product and promotion with my first chat before I concluded my order, why was I not told then that the promo had ended last month already and to please excuse the error and be told that said items will be charged at full price?

What annoys me the most is that whomever is handling the chat service is making it seem as though I'm demanding a promotion that has already ended that I did not bother to query prior to making payment. The live chat was the worst, I was patient with the operator whilst he was looking into my order but he/she ended the chat before I could respond and I'd like to believe that if on my screen it tells me when he/she is typing, it does the same when on his/her end. Surely he/she was aware that I was typing a response.

I fail to understand how I am responsible for false adverti*****t and or a technical glitche on your end. I'd like my refund as initially stated.

I'm no expert on consumer acts,laws,policies and legislations but this cannot be right.