The way Chesapeake & Potomac Telephone Co. officials saw it, the long distance bills to Bolivia were becoming more expensive than being there.

Since late last year, someone had been phoning Bolivia at night from the C&P administrative offices at 200 N. Glebe Rd. in Arlington -- calls that a C&P spokesman estimated cost between $6,000 and $8,000.

Late Monday night, prompted by a C&P security supervisor who said someone was using telephones on the second floor, Arlington County police entered the building and reportedly found two men in adjacent offices.

One of them, police said, was using a phone but hung up quickly when officers entered the room.

John Cassio, 19, and William Zurita, 20, Bolivians living in Arlington, were arrested and charged with petit larceny and breaking and entering in the nighttime. They were being held in Arlington Jail under $2,000 bond each.

C&P spokesman Webb Chamberlin said the company is continually investigating unauthorized calls, but he added that "it is unusual for someone to come into a company building, particularly an unauthorized person, and attempt to make calls and not pay for them. Generally speaking, you find people who make unauthorized long distance calls don't stay in the same place," and instead use various coin-operated telephones.

Chamberlin said the company attempts to collect on bills for unauthorized calls but that calls amounting to about 1 percent of C&P's total revenue eventually are written off as "uncollectible."

Chamberlin said it is not unusual for an investigation into unauthorized calls to continue for a long period before an arrest is made. It may take several months for a pattern of calls to emerge, he said, and then "you have to catch the people in the act."