Some cellphone providers are already getting the word out to their customers: 10-digit dialing will become mandatory for all calls you make as of May 14th — including local ones. It’s because a new area code, 826, will join the 540 region later this year. 10-digit local dialing is already possible, and you are urged to check your contacts and speed dials to be sure they all include the area code. More from WFIR’s Evan Jones: