While many numbers in Washington County could be reached Friday by using only seven digits, Arnette said the switch to 10 digits could take place at any time.
"The seven-digit call that goes through this morning might not go through this afternoon," she said.
Bell Atlantic is requiring that all calls in the state be made with the 10-digit combination of traditional seven-digit number plus area code so it can add two new area codes - 240 and 443 - to the state later this year.
But unlike every other state in nation, where each area code occupies its own geographic region, the new Maryland codes will be added to the same areas as the existing 301 and 410 codes. That opens the possibility of houses on the same block having different areas codes - a prospect that requires 10-digit local calls.
The phone company spent millions publicizing the switch to 10-digit dialing through billboards, newspaper ads and even children's coloring books during the past year. But the promotions did not mention the possibility that many local numbers could still be dialed with seven digits after the supposed deadline of midnight Wednesday.
"What a big fake," said Marvin Harsh, 65, of Williamsport. "This is false advertisement."
Harsh said when Thursday came he was determined to defy Bell Atlantic's order and stick with dialing seven digits.
"I keep getting through all the time," he said.
Arnette said one of the reasons the company did not switch all the phone numbers at once was because it could have caused computer problems and other logistical confusion.
She said the company purposely did not publicize the phase-in plan because it wanted customers to immediately start using 10 digits to make local calls.
"We didn't want people to get the false sense of security that they were going to get that grace period," she said.
And whatever grace period there is won't last.
"It's coming. It's coming your way," Arnette said.