Chesapeake & Potomac Telephone Co. is changing the face of the public telephone.

C&P is installing new credit-card phones that give customers access to the long-distance company of their choice by using any one of five credit cards, C&P said last week.

Because the new system bills customers through credit-card companies, customers can use long-distance services without being a subscriber with a direct billing account, said C&P spokesman Web Chamberlin. The ChargeAll phones accept American Express, MasterCard, Visa, Carte Blanche and Diners Club cards.

To use the "ChargeAll" phone, customers draw a credit card through a slot on the phone. The card number is automatically verified and recorded, and the caller is told to select a long-distance company by pushing one of several labeled buttons.

Customers can also gain access to American Telephone & Telegraph Co. by entering their AT&T credit card number on the touch-tone phones. Although the phones do not accept coins, they will provide customer access to operator assistance, 911 emergency and directory assistance.

Initially, C&P is installing 144 of the phones in Washington's National Airport and in Crystal City hotels. Newark Airport also has 144 phones, said Chamberlin. Bell Atlantic Corp., the C&P holding company, plans to install the phones in Baltimore, Philadelphia, Atlantic City and Pittsburgh.

MCI and ITT are the first long-distance services available through the public phones, but up to seven long distance companies will be available by the end of the year, a Bell Atlantic spokesman said.