SAN FRANCISCO (CBS SF) — Starting next February, San Francisco and Marin County residents will have to do something they’ve never done before: dial the numbers 4-1-5 when making a phone call.

In February 2015, Marin County will begin rolling out a new 628 area code for new customers. Existing customers will not have change their area codes.

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With the introduction of the new area code, all local callers will have to dial an 11-digit number to make a call, even 415 customers dialing within the 415 area code.

The 415 area code, which was established in 1947, includes San Francisco, most of Marin County and a small portion of San Mateo County, according to a Marin County news release.

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Officials are urging residents to begin to practice dialing 1-415 before their calls starting on August 16, even though local phone calls without the area code will continue to go through until February 21, 2015.

After February 21, callers who don’t dial the area code will receive an error recording instructing them to hang up and dial again.

The 628 area code will begin to be assigned to new Marin County telephone lines starting on March 21, 2015.

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