Cal. INS § 10192.55

(a) With regard to Medicare supplement policies, all insurers, brokers, agents, and others engaged in the business of insurance owe a policyholder or a prospective policyholder a duty of honesty, and a duty of good faith and fair dealing. (b) Conduct of an insurer, broker, or agent during the offer and sale of a Medicare supplement policy previous to the purchase is relevant to any action alleging a breach of the duty of honesty, and a duty of good faith and fair dealing set forth in subdivision (a).