This scam is a result of both cultural differences and vague terminology. In some cases, it may be an honest mistake, while in others, language is intentionally left ambiguous to confuse the customer.
The best example is the European double room.
In the US, a double room almost always means a room with two double beds. But in Europe, it could also mean a room with two twin-size beds, like a college dorm; or even a room with just one double bed.
Other issues arrive if you try to bring more people than you mentioned in your booking form, like if you book a room under your name but your spouse joins you, or if you book a "family room" but don't tell somebody at the front desk that you actually need multiple beds.
Russell said he has seen clients who booked their own travel arrive in Europe to find a room type different from what they thought they'd booked. While hotels may even acknowledge the ambiguity, he said he's "seen them refuse to accommodate their new needs or charge exorbitant fees for adding a person."
According to Russell, these fees should be somewhere in the fine print. If you have to change room type, though, many hotels will charge you the current rate for booking a whole new reservation.
"And they don't have to do you any favors there," he said.
Usually you can avoid this by looking closely at the rooms on their website. If that fails, call the hotel directly and ask.