The new requirement takes effect on Feb. 26 to help prepare for the new 531 area code. Utilities and state officials are working to remind people about the change, which has been in the works for several years.
Previously, area codes were only required when making long distance calls.
But the new 531 area code is being added to the same geographic area already covered by the 402 code. When officials run out of numbers in the 402 area code, they will begin issuing 531 numbers.