San Francisco and Marin, not the whole Bay
415 began in 1947 and has been divided as California’s numbering needs grew. Today it covers San Francisco, most of Marin County, and a small portion of San Mateo County. The 628 overlay became effective on March 21, 2015.
Both codes serve the same geography. Avoid treating 415 as the original local code for Oakland or all of Silicon Valley, and describe your actual service area separately.
Dialing and call prices
California’s guidance specifies 1 plus the area code and seven digits for this region. Some mobile providers accept the ten-digit form. Adding the area code does not itself make a call a toll call or change its price.
A customer’s provider and plan determine service and charges. Buying a 415 number does not buy a different network from a 628 number.
Compare identity with practical use
A familiar code may fit your brand, but the rest of the number still has to work. Compare full digit sequences, price, word clarity, and intended use.
A rate-center label describes numbering geography. It is not proof of where a caller is or where your business operates today.