In order to dial out of our service, calls must be made in accordance with the North American Numbering Plan (NANP) system. For example, calls within the USA must use 10 or 11-digit dialing, which means an optional 1, plus the area code and the remaining seven digits. For example, dialing 12158258792 or 2158258792 both work. "Local" 7-digit dialing will not work, but you can almost always configure a device's SIP dialing plan to handle 7-digit dialing.