The warehousing of these numbers by service providers is prohibited by FCC rules, because it is illegal for a subscriber to sell them. Referred to as 800 numbers, after the original area code, these numbers can also start with the area codes, 888, 877, and 866, however these area codes are not interchangeable with each other. Using these numbers is a great way to get your business rolling. Having a vanity 800 number is perfect for businesses that wish to generate additional business by having an easily remembered phone number. A toll free number represents that you are serious about your business.