Advertised promotion price not granted while checking-out

Hi,

I wanted to buy a privacy filter for my newly purchased Dell inspiron 14 7000 laptop which is advertised online at promotion price 34.99 CAD today march 12, 2019 (having a regular price of 54.99 CAD), see link  https://www.dell.com/en-ca/shop/dell-privacy-filter-140/apd/750-abek/monitors-monitor-accessories?re...

When I was going through online checking out  process it showed the regular price 54.99 CAD and not the promotion price 34.99 CAD as advertised. When chatting online with an agent, Dell didn't agree to grant me the advertised online price as of today 34.99 CAD,  saying that the price shown on the check out (54.99CAD) is the right price and it takes 24 hours to see this regular 54.99 CAD price advertised again online. And above all, the Dell agent chatter said to me: that she was willing to grant me the promotion price 34.99 CAD but The TOOLS don't permit to do so....I let the readers comment on this!!!!!  I am completely disappointed. Do you think this is right, respectful and honest way to deal with a Dell Loyal customer ? 

P.S. : I have just bought in January 3rd 2019 Dell Inspiron 14 7472 laptop; and by the way, I have just got  (11 march 2019) my pending advantage rewards.