Midland Funding Suing me for balance of repossesed vehicle, never heard of them San Diego California

I received a summons today to appear in court for an arbitration hearing involving a company called Midland Funding LLC who is being represented by a law firm called Blatt Hasenmiller Leibsker & Moore. I have never heard of or received anything from these people.

In 2004, I had to give up my Chevy Blazer because I could no longer afford the payments due to unemployment. Wells Fargo was the title holder and they sold the vehicle for alittle over $7000, leaving a balance of alittle over $14000, this was on March 16, 2004. The summons is saying that that there was a balance of $20,694.25 on Feb 2, 2004 and this is the amount they are suing me for.

One, why are they suing me, when they've never even sent me a bill, and:
Two, where did this 20694.25 come from when the receipt attatched to the summons clearly states "Total Amount of Deficiency $14338.83" Where did the other $6300 come from?

Is there anything I can do about this? I understand the 14338, but what can I do about the information that appears inaccurate to me?

Bob
highland, Illinois
U.S.A.