Citigroup will refund $330 million to credit card customers it overcharged

The company reports the average refund will amount to about $190 per account -- including interest.

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If you have been late on two consecutive credit card payments, an issuer can increase your interest rate. When you've made your minimum payment on time for the next six months, according to the CARD act, your interest rate is eligible for an interest rate reduction.

Half of the impacted Citi accounts did not receive that reduction at all. The other half received a reduction, but it should have been larger, according to Citi.