How to Handle Dyson Stock Discrepancies & Unfulfilled Promotions

We purchased some products from the company Dyson and are enjoying them. The company offered us a 10% discount if we purchase a new product. Thank you for their thoughtful gesture.
For approximately a month we have been trying to order the product “Supersonic Nural” with a travel-bag gift. But for a month they’ve been telling us there’s no stock, even though the product is listed as “in stock” in their online store.
We think such a tragicomic situation can only happen in Turkey. It doesn’t suit such a large company at all.
If I’m not mistaken, the promotion ends on November 1.
Please, let an official hear our voice.