Rob Gilbert recently thought he was buying some items online for himself and Charles Langstonsome gifts for his mom's upcoming birthday after clicking on an online ad for a major retailer.

But when Gilbert went to check out, he got a "card declined" message.

He didn't think much of it. It was a new card and he forgot the three-digit code on the back. Instead, he used his debit card number, which was stored on his phone, for the purchase.

But it turned out the Fort Collins, Colorado man's card wasn't declined after all.

It was a scam.

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Both cards were almost immediately used for fraudulent charges.

Fraudsters setting up fake sites

The Better Business Bureau is warning the public that an influx of consumers like Gilbert are reporting similar experiences to its BBB Scam Tracker.

Here's how it works.

Consumers reported shopping on what they thought was a legitimate website or clicking on an email or social media ad, which led them to a shopping website. Customers typically put in their name, address, email address and payment information.

But then customers said they received a "card declined" message or another that read "your card did not go through for some reason."

Thinking that maybe they made a mistake or they don't have sufficient funds, the consumer often pulls out another form of payment.

For many, they later get a real communication via email or text from their card issuer saying there have been fraudulent purchases charged to their account.

Gilbert, who also reported his experience to the BBB, said his first card was declined, but his second card went through with order and tracking numbers. But then he received notices that both cards were charged for $74.

His card issuer canceled both cards and refunded his money.

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Other consumers who reported the scam to the BBB said their cards were fraudulently charged $200 and $2,500 respectively.

“If you are shopping online and your card declines, resist the urge to use a different card," BBB spokeswoman Melanie McGovern told USA TODAY. "Instead, reach out to your bank to see if there is a problem.”

McGovern said if you suspect fraud, monitor your credit card transactions for any unusual activity and report it to the BBB's Scam Tracker.

Tips to avoid online purchase scams

Here' are some tips from the BBB to avoid online scams:

• Verify that the website is legitimate: Scammers often create fake, lookalike websites to trick shoppers into thinking they are buying from the actual business. Take a close look at the URL – it may be off by a letter or two – and check that the website is secure by verifying that you see "https://" in front of the web address.
• Watch out for fake emails, texts and ads: Scammers often impersonate businesses in fake emails, text messages, and social media advertisements. Don’t trust messages that come unsolicited and always verify a link before clicking on it. If you're in doubt, search for the business's website on your own.
• Don't be lured by great offers: If the price seems too good to be true, it could be a scam. Do some comparison pricing of the product you want.
• Research the business. Before purchasing, look up customer reviews online and search the business on BBB.org. You can also search on BBB Scam Tracker to see if it is a scam.
• Use a credit card for extra protection. Credit card companies offer additional protection against fraud so you should be able to dispute any unexpected charges on your account.
• Check your credit and debit card protections. Get up to date on what protections you have on your cards by contacting your bank or researching your protections. You can also set purchase limits, travel restrictions and set up notifications for when purchases are made.

Betty Lin-Fisher is a consumer reporter for USA TODAY. Reach her at [email protected] or follow her on X, Facebook or Instagram @blinfisher. Sign up for our free The Daily Money newsletter, which will include consumer news on Fridays,here.