Dropbox dark pattern offers fake discount the company won't honor

When signing up for a Dropbox plan, the site pops up an offer of a 25% "exclusive special discount", seen here:

https://www.dropboxforum.com/t5/image/serverpage/image-id/40...

In reality the offer just silently switches the selected monthly plan to the annual plan, or does nothing if you're already on the annual plan.

Several users have complained on their forum about this deceptive practice, and the company refuses to honor the advertised discount.

(They removed my post when I shared a link to the FTC Report Fraud website.)