Three of the state’s largest banks were sued.

A class-action suit filed Oct. 28 in Superior Court accuses Bank of America, Wells Fargo Bank and First Interstate of illegally conspiring to make more than $1 billion in excessive credit card interest charges over the last four years. The suit noted that First Interstate charges 21% a year on credit card balances, Wells Fargo 20% and Bank of America 19.8%. The suit was brought by two law firms in San Francisco and two in San Diego on behalf of 1 million California residents holding credit cards issued by the defendant banks.