Special offer not made known to customer

Debonairs has a special running R199.90 for a triple decker cram crusted, which is the same price as a triple decker, now because I didn’t have my glasses I did not see the poster for this so I ordered my triple decker as usual. Now common courtesy/good customer service would be to let the customer know of the special, she could have let me know if I would like it cram crusted instead, at no extra cost. On top of that she was rude, I greeted her twice before she somewhat greeted back. Now I know she is not obliged to, but most tellers at most shops do let me know when they see Im purchasing something where I could either save money or get something free. I’ve experienced this at shoprite, dischem, spar, food *****s, pep, mr price, pnp, mcdonalds, king pie, best of asia chinese food takeaway etc.