the issue is you're complaining about a fault with you, and blaming it on someone else. The fact you're not taking responsibility is why you're being dragged through the mud.
your post should be "oops, I forgot to use a coupon like a normal person and forgot to ask the store if they had any deals. look what my stupidity got me!" and you'd have some chuckles and some commiserations.
Instead, you're trying to blame Domino's for you not knowing that coupons have existed since the 1800s or something.