What can I do if the foreclosure attorney won't return my messages?

Did the first attorney charge an up front fee? If so, he violated the law and you are entitled to a full refund regardless of whether he did any work for you. Refusing to respond to client communications is itself a separate violation of the Rules of Professional Conduct. You should file a formal complaint with the State Bar of California. In the meantime, you should hire a different attorney right away so you don't lose any rights.

If you are sending information to the bank's attorney and they won't respond, perhaps they are expecting you to present your defense in litigation. Hopefully, they sent your defense information to their client, the lender, but that does not excuse you from defending the case in Court if there is pending litigation.