The change is meant to help customers transition to the addition of the 930 area code in southern Indiana.
Residents living within the current 812 area code region will have to dial using 10 digits starting Sept. 6.
The recommendation means new phone numbers would have a different area code, while existing numbers would keep the 812 code.
Residents say they would rather have two different area codes in the same region, than force some Hoosiers to get new phone numbers.
The 812 area code for Southern Indiana is set to run out of numbers by 2015.