Police are investigating the actions of scammers who make thousands of international and premium rate calls.
The fraudsters are able to break into telephone lines from a remote location, and a telecommunications management company believes it is real concern for businesses in the region.
"One Belfast firm lost £10,000 in just one weekend while one in North Down another was scammed to the tune of £3,000," warned David Beatty from Rainbow Communications.
"It is the business that is solely responsible for the fraudulent call charges so it really can have a detrimental effect on any firm in Northern Ireland."
This type of phone hacking is a real and serious concern for businesses in Northern Ireland.
Companies can be targeted by scammers who gain access to a switchboard or take out a phone service in a fake name and leave a bad debt.
"Fraudsters are making thousands of international or premium rate calls resulting in substantial costs at the expense of the unsuspecting company," added Mr Beatty.
NI-based businesses have been targeted in the past few weeks but, globally, losses due to phone frauds cost almost £10bn a year.
A spokesperson for Action Fraud encouraged any business targeted by phone scammers to report the crime.
Businesses are also advised to be vigilant and take steps to thwart potential scams, including barring unnecessary international or premium rate numbers and limiting after hours calling.