https://www.dir.ca.gov/dlse/california_equal_pay_act.htm
This FAQ for the law in question has a link for complaints. It's an equal pay act violation.
- Where and when can a person file a claim if they were aggrieved by a violation of Labor Code Section 432.3?
The person may file a complaint with the Labor Commissioner’s Office, the state agency charged with enforcement. A written complaint must be filed within one year after the date the person learned of the violation.