The collection agency and the orginator never notified me of my requirment

I sent the attached debt validation letter to an agency. The collection agency and the orginator never notified me of my requirment to pay this debt. I was never sent a letter or notice. When I sent the letter to negotiate with the orignator they said they showed I owed the money. They did not have any documentation that I did not pay or for the book. They said they had the incorrect address and when it came back to them they just sent the account to collections without trying to find out another address. The collection agency sent me a letter back with computer printouts of the school showing I owed money for the book, that my tuition was paid, and that I took the class, but no real proof that I owed the money for the book. What would you suggest I do now?
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was the book honestly not paid by you
how much is the collection you could negotiate payment and removal if you pay in full.
if the account is small i would suggest this route to be done with it sounds like they may not have validated the debt
also
might send the debt validation follow up letter
moving and finding addresses is one reason they have credit reports
that way creditors do not have to spend more than it is worth to hunt some one up they just slap it on your report and it goes where you go