The US mobile operator said that the account in question had been inactive for several months, and is for a standard mobile rather than an email or data-enabled device such as a BlackBerry.
Until Verizon can distinguish between those employees who have a legitimate reason to access the details, and those doing so for their own interest or possible illicit gain, every employee who has recently accessed Obama's account has been put on immediate paid leave.
"As the circumstances of each individual employee's access to the account are determined, the company will take appropriate actions," said Lowell McAdam, president and chief executive at Verizon Wireless.
"Employees with legitimate business needs for access will be returned to their positions, while employees who have accessed the account improperly and without legitimate business justification will face appropriate disciplinary action.
"We apologise to president-elect Obama and will work to keep the trust our customers place in us every day."
Obama was recently told that he may have to give up his beloved Blackberry as the Presidential Records Act requires the White House to log and archive every email the president sends, and make the messages available to the general public.