The trick is called 'phone spoofing.' It's a tool used by fraudsters to mislead people into thinking the call is from a reputable business or person.
Sometimes the number the scammer uses already belongs to a real person.
Mike Boychuk, a real estate agent in Saskatoon, has been a victim of phone spoofing.
It all began last year when Boychuk started getting suspicious calls with the Saskatchewan 306 area code coming through on his work cell phone, personal cell phone and home number. When he would answer, an automated voice would inform him he had won a cruise or offer an exclusive deal on air miles.
"I'd get a call from a local —what appeared to be — cell phone," Boychuk said.
Boychuk told CBC News he tried to ignore the calls, but a couple days after the calls started, regular people started calling him.
"I started getting people phoning me... they'd say 'I'm just calling you back', and I'd say 'who is this?'" Boychuk said. "I thought it was really strange because I hadn't made any calls."
After these sorts of calls persisted, Boychuk contacted his cell phone carrier, Telus Mobility.
Boychuk said Telus told him he was a victim of phone spoofing and assured him that the scammers usually used a particular number for only one or two weeks before they'd move on to another.
Telus Mobility media representatives were not available for comment when CBC News tried to reach them Tuesday morning.
Boychuk said the calls still come on a regular basis.
"They do not quit ... It's about driving me to the brink of sanity because they call every number I have, my two cell phone numbers and my home number, maybe, at least twice a week," Boychuk said.
Canada's Anti Fraud Centre said victims of phone spoofing should immediately call their phone company when they realize what is happening.
"Your telephone or Internet service provider may have the ability to determine the true IP address or telephone number but they must be informed quickly before this information is overwritten on their database," Canada's Anti Fraud Centre explains on its website.