will they keep doing this?

I am curious about something, I have a car that I was buying and I had to do a voluntary repo on it. I tired to work out something with the company to get the payments lowered to something I could afford as I lost my job about 3 months later. The original creditor started calling and harrassing me, asking me all kinds of questions that had nothing to do with the loan etc.

I have not made any payments since June 06, I think and I have gotten letters from 4 or 5 different collection agencies now saying I owe this debt. My credit report shows it as a write off, (not sure what that is). Every time I get a letter from a collection agency I send a validation letter to them and I get nothing back. One did send me a copy of my contract, but nothing else and could not explain how they got the extra $5,000 it shows me owing, then sent it on to a different CA.

So I am just wondering if this is going to continue and for how long, I send a validation letter and a couple months later a new collection agency has the debt and is trying to collect. Do I just keep sending validation letters until the SOL expires which I think is in two years. When I tired to work out some type of payments with the original creditor they would not work with me. My only income is disability and child support which I don't think they can garnish if I am correct. Should I be worried about this or just let the CA keep buying the loan and getting nothing from me as they can't validate anything. Thanks.