Is there anything I can do about missing attorney?

[familyof7]

What is the name of your state? California
Any advice would be greatly appreciated. We retained an attorney to file Chapter 13 bankruptcy, he was paid in full. Several months later we saw him to have our payments modified. He assured us that it was no problem and gave us a new $amount to pay monthly. We did this for several months until the trustee sent us docs saying that we were not paying the full amount. We explained that our attorney, Mr. Koulouris had filed a payment modification. Apparently he never did and our case was discharged. Since then, Mr. Koulouris has not returned any phone calls, faxes, e-mails or letters. His office is now gone and I have just found out that he has started some digital music company with his brother and is now their attorney. (This was found out by looking for him on the internet.) We've tried to reach him there, but he has not called back. Now we have creditors threatening us and are out of the $ we paid him. What can we do? Can we sue him? Thank you!