California debt collections creditor's statute of limitations

Hello,
I have received a phone call from a collection agency trying to collect a dept from a Car Towing Company in California.
The Tow was executed in error but I have never been able to win my disputes.
The tow took place back in October of 2002 and I have not heard from the collection agency in five years. Also, I was never informed by the towing company of the status or location of my car. I have found out that they sold my car after forty days being in storage on their lot.
None of the parties involved are and were willing to help and even listen to my explanations.
It has affected my credit score.
Since I have not been able to communicate with any party involved how shall I proceed and what is the statue of limitations for the collection agency to harass me and how long will it affect my credit?
Thank you