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The Consumer Financial Protection Bureau will be a year old July 21. Its complaint database has been live six weeks and registered 1,549 cases, or about 31 a day. So far, Capital One (NYSE: COF) has gotten the most complaints while bluechip American Express (NYSE: AXP) has been nearly unscathed.

The database offers the public an easy-to-use interactive snapshot of the types of problems credit-card customers have had with the largest card issuers.

As one would expect, banks with the largest number of cardholders also have the highest volume of complaints, but this isn't true across the board.

For example, American Express had the highest number of transactions in 2011, at $519.5 billion in purchase volume, according to The Nilson Report, making it the No. 1 credit card handler; but it has received the third-lowest number of complaints among the country's top seven banks in terms of volume of credit card transactions.

The seven top banks that received over four out of five of the complaints registered so far on the CFPB's database handled $1.7 trillion in credit card transactions last year -- about 83 percent of the total of $2.05 trillion -- and ended 2011 owed $535.2 billion from people who carry debt on plastic.

There are 32 types of complaints in the database. The most common issues included billing disputes, overdraft or other fees, annual percentage rate (APR) rate adjustments or credit reporting conflicts. Here are the top seven offenders.

Coming in at No. 1, Capital One so far has received 335 of the registered consumer complaints, or 21.6 percent of the total.

The bank was the fifth-largest handler of credit card purchases last year with $115.6 billion in purchasing volume, and it was the fifth-largest holder of outstanding credit card debt, $50.9 billion, at the end of 2011.

At No. 2 is Citigroup Inc. (NYSE:C). Customers have so far registered 267 complaints, or 17.2 percent of the total.

Citibank was the fourth-largest handler last year, at $194.6 billion, and it ended 2011 with $92.3 billion in outstanding credit card debt owed to it. The bank ended last year in third place in terms of money owed to it by credit card users.

JPMorgan Chase & Co. (NYSE:JPM) came in a close third in terms of complaints filed to the CFPB so far, at 247, or 15.9 percent.

Chase is ranked as the second largest credit card lender in terms of customers' purchases ($370.8 billion) and is the No. 1 bank owed money from cardholders as of the end of 2011, at $130 billion.

Bank of America Corp (NYSE:BAC) has been the target of 202 registered complaints, or 13 percent of the total, which puts it in fourth place.

BoA was the third-largest credit card transaction handler last year at $248.6 billion, and was the second largest in terms of outstanding debt owed by cardholders at $112.6 billion.

Complaints against American Express, the largest handler of credit card transactions last year, and the fourth largest holder of outstanding credit card debt ($80.2 billion) at the end of 2011, represents 5.9 percent of the total, or 92 complaints so far.

Discover Financial Services (NYSE:DFS) was the sixth-largest hander of credit card transactions ($100.1 billion) and it held the sixth-largest amount of outstanding debt ($46.6 billion) as of Dec. 31. It also ranks sixth in terms of registered complaints at 74, or 4.7 percent of the total.

US Bancorp (NYSE:USB) has 26 complaints registered against it, or 1.7 percent of the current total. The bank handled $84.5 billion in transaction volume and had $22.6 billion in outstanding debt from its credit card customers by the end of last year.