CHICAGO - The Illinois Commerce Commission reminded consumers Thursday that the city of Chicago, presently served by area codes 312 and 773, will get a third area code beginning Saturday, Nov. 7.

The 872 area code will overlay the 773 and 312 area codes to supplement the telephone number supply and will require 11-digit dialing in the city.

All calls must be dialed 1+ area code + telephone number. Residents will no longer be able to dial seven digits to a local number inside their area code. Residents are reminded that their phone number will not change.

With the 872 area code, current customers will keep their existing phone numbers as well as their 312 or 773 area codes.