Effective Saturday, southwestern Ontario communities including Sarnia-Lambton will be getting a third area code.
The new 548 number will be introduced alongside 519 and 226 to deal with increased demand for phone numbers.
Canadian Numbering Administrator spokesman Glen Brown says people with existing numbers won't be impacted.
"It also doesn't mean that you still could not get a 519 number," says Brown.
"Unfortunately, people pass away or move and businesses go bankrupt. Those numbers go back to the assignment pool, they get aged for a little period of time, and then get released back out. So those numbers will still be in circulation."
Brown says the introduction of the 548 area code will open up millions of additional telephone numbers.
He stresses that 9-1-1 service and how you place local calls will not change.