Commerce Bank hiked the interest rate on Mira Tanna’s credit card to 20 percent – without telling her. Once she figured out what the bank had done, realized what happened, Tanna decided to make use of the Consumer Financial Protection Bureau’s new online complaint database, which had just gone live. “Why not try submitting a complaint and see what happens?” she reasoned.

What happened was a $1,044 refund and an interest rate reduction to 8 percent – lower than Mirra had requested, she told reporter Becky Yerak of the Chicago Tribune.

“For the first time, I felt the strength of this new watchdog,” Tanna said.

The Tribune analyzed the database’s more than 13,000 complaints (as of October 2012), and found that nearly a third involved interest rates and billing disputes. “Through the site, consumers may let the world know about problems they’re having with their credit card companies,” Yerak writes, “Others may poke around on the database to get the skinny on which card companies are being criticized, for what, and how quickly they’re resolving the problems, including whether monetary relief was given. The database includes consumers’ ZIP codes, but it doesn’t share any names or addresses, and no narrative is provided from consumers or credit providers.”

Banks have objected to the posting of statistics on unverified complaints. Consumer advocates, on the other hand, “say that the site, which consists of dryly presented data and text, could be livened up by adding narratives for each complaint, a la Yelp or Amazon,” Yerak writes.

The database marks a big step forward for consumers who earlier might have found their complaints going into a “bottomless well,” AFR Executive Director Lisa Donner told Yerak.

“In many cases, this not only produces responses to the consumers, but also gets them some money back,” Donner said. “We urge the CFPB to take the next step to make the narratives public as well, as that would make the database even more useful.”