Adam Dooley knows a scam when he hears one, but lately, scammers have added a new twist to get Winnipeggers like him to pick up the phone.

Dooley received two calls in two hours recently, telling him he had won a trip through Shoppers Drug Mart, from what appeared to be a local number.

"This is what's so frustrating and what's so sneaky about it," he said.

"You think it's a legitimate call and it's not."

Shoppers Drug Mart has posted a notice on its website, warning customers that the calls are a phone scam.

Daniel Williams of the Canadian Anti-Fraud Centre says scammers use computer programs to make calls look as though they are coming from local numbers. It's a technique known as "spoofing."

"Unfortunately just about every crooked telemarketer has access to it and uses it quite regularly," he said.

Williams said scammers use "any and every legitimate technology" to pry personal information from unsuspecting victims.

"Scammers find a way of twisting it to their own ends and of course caller ID 'spoofing' is fantastic for them because they don't want the victim to know who is calling them," he said.

Nathaniel Jankowski, 17, said he was surprised to learn his phone number was being used without his knowledge.

"It made me feel kind of mad and also … uncomfortable, knowing that I have my number out there and it's part of a scam," Jankowski said.

Williams said spoofing is another reason to be extremely cautious about giving out personal information over the phone.