Charged full price on substituted item

ORDER NUMBER O***, this order number was processed on 12 December 2022.

The Mini Shortbread Biscuits in Tin 300 g Tin was out of stock, and it was substituted with Chocolate Chip Cookie Duo in Amy Ayanda Design Tin 350 g.

This was part of the festive food deals, buy 3 items and get 20/25% off, I was charged the full price on the substituted item - Chocolate Chip Cookie Duo in Amy Ayanda Design Tin 350 g.

The Chocolate Chip Cookie Duo in Amy Ayanda Design Tin 350 g, it was substituted with was also part of the festive deal so this should have been discounted on the order.

I have sent emails on the 12 December 2022 to ***, *** AND *** and have had no response, going now almost two months.