Ok.. so a collection agency calls me and said they were looking for money from an account in 2000... can they actually do that.. it was never on my credit report?? It was at one agency and they passed it to another.. can this be done??

Unfortunately yes,

My parents passed away in 2001, they had a cell phone. The cell phone company has been hounding me for 7 years now for $234.00 to close the account. I have told them repeatedly that my parents are deceased, one id**t actually asked to speak to my mom or dad so that they could confirm this claim, what part of dead don't they get. This has now gone to a collection agency and they are still calling, I've even sent them a copy of the death certificates, they want originals. I finally told them last week that they should sue my mom and dad, or totally mess up their credit rating. Their response, "don't think we won't do it!"

Good luck to you.

Yes, they can and will call, If you owe it they will continue to bother you and morally you will always owe it until it is paid but depending on what state you are in the sol may apply
So legally it may not be enforced I am surprised that they have not gotten a judgement since this was from 2000

Yes, they can keep writing you letters and trying to collect as long as you live if they want. There is just a limited amount of time they have to sue you in court to get a judgement