Gift cards are a popular item over the holidays and are often tucked away and not used for a while. But one holiday shopper discovered the hard way how thieves are stealing the money off those prepaid gift cards and unsuspecting consumers are paying for it.

Alysia Stansfield bought a $150 Vanilla Visa card for online Christmas shopping. But when she opened the package, she noticed something was off. It appeared the packet had been tampered with and there wasn’t even a Visa inside, but rather a Mastercard.

“I didn’t notice it when I was buying it,” she said.

Turns out someone had carefully slit open the package, took out the Visa card, photocopied the barcode on the back of it and pasted that barcode back into the window of the package. The package was then returned to the shelf at the store.

These types of prepaid cards aren’t activated until the barcode is scanned by the cashier, so the thieves wait for an unsuspecting buyer to purchase them and activate the funds.

"I think someone's holding the cards at home waiting for them to be activated and going and spending the money," said Stansfield.

Fortunately, Stansfield had her receipt and went right back to the Surrey Walmart where she purchased the card.

When she looked at the prepaid cards on the shelf, she discovered at least five more packages that had been tampered with and placed back on the rack.

The company that issues the prepaid Vanilla Visa card told CTV News, "We have protocols in place to work with consumers, merchants and law enforcement to investigate issues."

Walmart took the rest of the Visa cards off the shelf telling CTV News that in most cases a new card is issued and mailed directly to the customer.

Stansfield did get a replacement and says she’ll carefully check the packaging if she ever purchases another prepaid credit card.

Ways to make sure your card hasn't been tampered with include:

Checking for glue residue and colour distortion on the package

Examining the barcode closely

Looking for slits along the seams

Since impatient thieves will often put the prepaid cards they’ve tampered with back on the front of the rack, pull a package that is less accessible from the middle of the rack. Or rather than buying a gift card that is hanging by the cashier, grab a card from a less-frequented area of the store.

Or another way to avoid issues is to avoid prepaid cards altogether. Instead give cash for gifts, or use other online banking options when shopping online.