Starting on Sunday, Oct. 24, all phone calls on the Peninsula-- even local ones -- will require the three-digit area code, the FCC announced. The 650 area code is one of 82 across the country making the switch.

In California, you may also need to dial 1 before the area code, according to the FCC.

The rollout of a new three-digit number to reach the National Suicide Prevention Lifeline is the reason behind the change. Last year, the FCC established 988 as the nationwide three-digit phone number for the service which will be available nationwide by July 16, 2022. It "will provide an easy to remember and easy to dial three-digit number to reach suicide prevention and mental health counselors, similar to 911 for emergencies and 311 for local government services," the FCC said in a statement.

Callers needing help are advised to continue using the old number, 1-800-273-8255 (1-800-273-TALK) during the transition period.

According to the FCC, on and after Oct. 24, local calls dialed with only seven digits may not connect, and a recording will inform you that your call cannot be completed as dialed. If that happens, hang up and dial again using the area code and the seven-digit number.

A full list of affected area codes is online here.