California law requires attorneys who handle client funds or funds entrusted by others to hold them in one or more interest-bearing bank accounts labeled as a "Trust Account," or words of similar import.
As advisor, a lawyer provides a client with an informed understanding of the client's legal rights and obligations and explains their practical implications. As advocate, a lawyer zealously asserts the client's position under the rules of the adversary system.
All you would need to do is notify your current attorney that you would like to terminate services, ask for a detailed final bill, and have your retainer balance returned.