An additional phone number assigned to an existing phone line in order to save a caller long distance fees. For example, a virtual number with a Boston area code can be assigned to a phone line in Phoenix or to a phone line in most cities in the world. The Boston caller pays no long distance charges and thinks the party being called is local. Virtual phone numbers allow call centers to operate 24 hours a day and advertise local phone numbers to each global market they pursue. Any fees associated with virtual numbers are paid to the telephone carrier or VoIP provider by the subscriber of the phone lines. See SIP provider.