My former employer has not returned my phone calls for mailing my last couple paychecks. What can I do to resolve this?

If upon your resignation you designated the place to which your final paycheck should have been sent, and the employer has refused to send your final paycheck to that address, you may have a claim for those wages plus waiting time penalties. The waiting time penalties will be awarded if it is found the employer willfully failed to pay your final check as required under the Code.
When an employee quits under the circumstances you did, the employer was required to send the final paycheck to the address designated by the employee within 72 hours of the notice of quit. Every day beyond that the employee is required to wait to get the check the employee becomes entitled to a penalty of one day of pay at your regular rate. There is a thirty-day limit on the waiting time penalties that can accrue.
You can enforce your rights in one of several ways. One is to hire an attorney to write a demand letter for you and negotiate a final resolution. One is to file an administrative wage claim with the California Division of Labor Standards Enforcement. Another is to file a lawsuit.
Good luck to you.

Sounds like you would have a claim for wait time penalties. Call the local labor commission office. Good luck.