Legal Question in Employment Law in California

In general, unless you are in a union or have a written employment contract, you are an 'at will' employee that can be disciplined or fired any time for any reason, other than 'illegal' discrimination under the Civil Rights, or Whistle-blower, or similar statutes. In your case, the employer has serious complaints brought against you, which provide more than adequate reason to terminate any employee. Your claim they are false, or that you can 'explain' them differently, does not mean the employer must take your word for it or disregard them. If you could prove through substantial credible evidence that you are completely 'innocent' and that all allegations are entirely fabricated and completely untrue, and if you provided all that evidence to the employer when confronted with the allegations before termination, then you might have a right to feel the firing was unfair. But, unfair is not 'illegal', nor does it make for a valid or meritorious case regarding termination. IF you could prove false statements were knowingly made against you with allegations of criminal or immoral conduct, then you could consider suing the person for 'slander', but the burden of proof is on you to prove all the above to a legal standard.