Mandatory 10-digit telephone dialing (three-digit area code plus the seven-digit phone number) begins Sunday for all residents in the 757 area code.

Local calls made with just seven digits will not be connected as of that day. It’s the second step in a February 2020 relief plan approved by the State Corporation Commission to phase in a new 948 area code. Permissive 10-digit dialing for the 757 area code region began Sept. 11.

In coming months, the inventory of available phone numbers with “757” as the area code is expected to run out. The SCC approved an overlay, which is the addition of another area code (948) to the same geographic region served by an existing area code (757).

Beginning May 9, new telephone lines or services may be assigned numbers using the new 948 area code. The good news: Residents and businesses that already have phone numbers will get to keep them. No one’s 757 phone number will change.

Alarm, security and elevator services and equipment currently located in the 757 area code and programmed to dial only seven digits must be updated or reprogrammed to dial the area code plus telephone number.