03/18/2010 05:12 am ET Updated May 25, 2011

872 New Chicago Area Code Goes Live This Week

Beginning on Saturday, Chicago residents will start having to dial 11 digits to make local calls.

With the addition of Chicago's third area code, 872, callers will have to dial one of the city's three area codes plus the seven-digit local phone number (along with the requisite 1), even if calling someone within the same area code.

The third area code is coming online Nov. 7 to help alleviate a phone number shortage, according to the Illinois Commerce Commission and the City of Chicago. It will overlap with areas already covered by the 312 and 773 area codes.

No one's current phone number will be affected by the new area code, and there are no charges for calling between the three area codes.