Can a collection agency continue to try to collect on an old apartment debt from 2000?

They have contacted me regarding a debt from 2000. They only provided me with a copy of my application and a copy of the apartments detailed charges. They cannot provide me with a copy of the lease where I signed stating I agree to pay them anything. Can this collection agency continue to pursue me? What should I do if they cannot find the lease I signed? This is also a shared debt and they are sayingif I pay half they will ';release'; me and it willcome off my credit report. She told me a RELEASE comes off of your credit for good.is this a lie?