Most of Alexandria and parts of Arlington last weekend became the eighth area in Northern Virginia to receive improved telephone service when C&P Telephone Co. Converted five telephone exchanges to the new electronic switchboard system (ESS).

The $7 million conversion not only speeds calls, giving almost instantaneous dial tones and immediate connections, but it makes special options such as conference calls and forwarding calls available for the first time to local phone users, according to phone company officials. The five extra options cost a total of $7.40 a month, and each can be purchased separately.

Conversion to the automated EES began more than a year ago and now includes areas near Herndon, Annandale, Falls Church, lewinsville, Barcroft and parts of Arlington.

The system is to include all of Arlington in the coming year as well as areas near Springfield and Merrifield, according to phone company spokesman Les Phillips. In 1982 the system will be implemented in Sterling Park; in 1983, Vienna and Centreville; and in 1984, the rest of Falls Church, Phillips said.

Some areas are not presently scheduled to receive the EES system, including Great Falls, Franconia and Centerville, Mount Vernon and Gunston, and some small sections of Alexandria.

The options available under EES includes: call-forwarding service, by which calls to your regular number can be transferred automatically to the phone of a friend or relative ($1.59 a month); speed calling, by which eight to 30 frequently called numbers can be rung by dialing only two digits ($1.59 to $2.64 a month); three-way or conference calls ($3.17 a month); call-waiting, which indicates by a tone that someone is calling your number and allows you to put one call on hold and receive the other ($3.17 a month).