A technician mistakenly cut off the home phone line of Greek premier George Papandreou while trying to disconnect a customer behind in payments.
The other customer's number was the same as the prime minister's, apart from one digit, says telecoms firm OTE.
The telephone line, in a suburb of Athens, was reconnected two days after it had been cut.
Mr Papandreou is under pressure to get Greece's debt-laden budget in order.
His government is pushing through unpopular spending cuts in return for a massive EU and IMF bail-out.
The OTE telephone firm says the technician's mistake, which happened earlier this month, was not spotted immediately.
"It was not a red phone," an OTE worker told the BBC, meaning that it was not one of Mr Papandreou's priority lines.