California Code, Civil Code - CIV § 1747.50

(a) Every card issuer shall correct any billing error made by the card issuer within two complete billing cycles, but in no event later than 90 days, after receiving an inquiry.

(b) Any card issuer who fails to correct a billing error made by the card issuer within the period prescribed by subdivision (a) shall not be entitled to the amount by which the outstanding balance of the cardholder's account is greater than the correct balance, nor any interest, finance charges, service charges, or other charges on the obligation giving rise to the billing error.

(c) Any cardholder who is injured by a willful violation of this section may bring an action for the recovery of damages.  Judgment may be entered for three times the amount at which actual damages are assessed.  The cardholder shall be entitled to recover reasonable attorney's fees and costs incurred in the action.