In California, the law gives you the right to choose your pronouns as you wish. You are totally free to request that people refer to you as he, she or they. You also have the right to change your name and to request others to call you by it. That does not mean that everyone will do it, however.
Some people just find it difficult. They may have gotten so used to addressing you in a certain way that even though they try, they still get it wrong sometimes. Your best option here is probably to be patient and hope it sinks in eventually.
Others, however, may do it on purpose. They may insist on calling you by a name or pronoun you no longer use. Alternatively, they might use your chosen name or pronoun but pronounce it in such a way, that makes it clear that they do not approve.
The law allows you to take action
One thing you might not have known is that you have options to address this refusal to call you by your name or use your chosen pronoun. Both fall under the category of intentional misgendering. Recently published guidance from the U.S. Equal Employment Opportunity Commission (EEOC) has made it clear that intentional misgendering is not acceptable. It amounts to sex-based discrimination based on your gender identity, which Title VII of the Civil Rights Act does not allow.
Employment laws are continually adapting. Be sure to learn more about the current situation if you feel someone is discriminating against you because of your gender identity or any other protected characteristic.