A new area code coming to parts of New Jersey next month has changed the way people dial.

Starting Saturday, residents in central and southern New Jersey, as well as the Jersey Shore, now must dial 10 digits instead of seven to make a local call. The extra digits are to make room for a brand-new area code -- 640. It's being added to areas that are currently using 609, such as Trenton, Princeton and Atlantic City.

The state Board of Public Utilities stated it's a necessary change because the 609 area code has run out of new numbers. That's because of the influx of people moving into area.

This process, known as an area code overlay, does not require customers to change their existing phone number but does require them to dial the area code and the seven-digit telephone number on calls within the same area code.

Phone numbers for the new 640 area code will start being issued on Sept. 17.