Washingtonians, get ready for a new area code.

T-Mobile is letting customers know that a long-planned additional area code for western Washington State — 564 — is coming in 2017. In addition, soon people will have to punch in both the seven-digit phone number and the area code to complete a call. Though in the age of smartphones, most of us already do that.

The new area code overlay, which was originally approved in 2000, will start in western parts of the state that fall under the 360 area code, eventually expanding to Seattle (206), Tacoma (253) and Bellevue-Redmond (425) once number combinations in those areas are exhausted.

This story has been updated to correctly reflect Tacoma’s area code.

The new 10-digit dialing procedure goes into effect Jan. 28, but calls from Western Washington using seven-digit numbers will still be completed until late July. After that, all calls will require the area code and phone number to go through.

New telephone lines using the 564 area code will debut in August.