I need an answer NOW!!! PLEASE!!!

If I disputed a debt for the amount a collection agency is saying I owe and they do not validate the debt for 6 months. I then file suit against them and they sent me a letter stating I made payments on the account and they are not required to validate a debt. But the letter they sent does have a different amount owed (its less) then what they have been attempting to collect (still more than what I think I owe) is this FDCPA violation. I have disputed the debt with the credit agencies and their investigation yeilded verified no change for the CA. They CA still has not placed the account is disputed by consumer on my credit report. Is this a defense in cour that the agency changed their amount they say I owe and does validation work for an improper amount owed on a debt? I NEED CASE LAW support. FDCPA verbage and status.