Original sentence: For example, in North America calls to the 800, 888, 877, and 866 areas are free to the caller and paid by the receiver, while calls to the 900 area are "premium rate", which means "more expensive"
Edited sentence: For example, in North America calls to the 800, 888, 877, and 866 areas are free to the caller and paid by the receiver, while calls to the 900 area are "premium rate", which means "very expensive"