Residents of the Conejo and San Fernando valleys will soon need to change the way they make their phone calls.

Beginning April 18, all calls within the current 818 area will require 11-digit dialing. Callers will need to dial 1 plus the area code plus the phone number.

Due to a shortage of 818 area code telephone numbers, the California Public Utilities Commission voted last year to create an overlay map for areas that now use the 818 area code.

All customers who currently use the 818 area code will keep it, but new customers will be assigned a 747 area code beginning May 18.

After April 18, dialers who don't dial all 11 digits will hear a recording instructing them to hang up and call again.

What's considered a local call now will remain a local call, regardless of area code. Prices of calls or other rates and services won't change due to the overlay.

The 818 code was put into service in 1984. It stretches over the San Fernando Valley and small portions of Thousand Oaks and Pasadena.

Prior to approving the area code overlay, the CPUC held public meetings in Calabasas, Burbank, San Fernando and Van Nuys.

According to the feedback they received, more preferred an overlay to a split, which would require about half of the people residing in an 818 area to change their area code to 747.

For more information, visit www.cpuc.ca.gov/818areacode.

—Joann Groff