If you have a 925 area code, beginning on October 24, 2021, you must dial ten digits (area code + telephone number) for all local calls. On and after this date, local calls dialed with only seven digits may not connect, and a recording will inform you that your call cannot be completed as dialed. You must hang up and dial again using the area code and the seven-digit number.

Details and more information are available at the FCC website here