Misleading pricing, bait and switch, stick you with charges you did not agree to.
They were not able to provide me a round-trip ticket for the price they quoted, but said that since they've already purchased the tickets for one leg of the trip, I have to pay for it, even though they can't deliver the total trip for the quoted price. Then tried to upsell me on more expensive return tickets, refused to refund the charge I did not agree to, refused to connect to supervisor. The bit about them already purchasing one leg of the trip also turned out to be a lie, according to both the airline and the credit card company.