CHICAGO (CBS) — Fraudsters live for the kind of envelope a Romeoville woman got in the mail. She said it was filled with detailed account information, from other people.

She also said when she called the bank, it took a while for anyone to get on the case.

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She explained to CBS 2’s Kristyn Hartman why that troubles her.

“At first, I had to do a double-take,” Gina Mershon said.

Inside the Chase Bank envelope, Mershon found a letter to her about a charge dispute. And there was more.

“The rest of the 11 pages were other customers’ information, details and all,” she said.

The paperwork contained addresses, and what appeared to be full credit or debit card account numbers for at least three Chase customers.

Mershon also received partial information on a woman who lives in Lincolnwood.

That woman didn’t want to be on camera, but she did say she is concerned about the situation.

So is Mildred Mullett in California. She confirmed one of the account numbers a total stranger got the mail is hers.

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“I am mad. I’m mad and I’m upset. I mean, I don’t know for sure what’s going to happen next,” Mullett said.

Chase Bank, which admitted an error, said “We will contact the affected customers, alert them to the issue, apologize and provide free credit monitoring for a year.”

The response came two days after Mershon called Chase about the account numbers in her possession.

“Time is definitely of the essence in a case like this, because the fraudsters don’t need any time at all to get online and start doing their dirty work with your account numbers,” said St. Xavier University fraud expert Professor William Kresse.

“I could have gone on eBay and had a spending spree,” Mershon said.

Asked what is her overriding concern, Mershon said “that my credit is compromised.” Because if she got someone else’s info, maybe somebody else got hers.

She’s closing her Chase account.

Mullett has the same plan. She’s mad her information was out there, and she said she’s angry because Chase Bank staffers she spoke with in California denied there was an issue.

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Officials in Illinois said they’re correcting the error, and reviewing why it happened, so they can fix any issues.