Are you 100% sure that the debt is wthin SOL? Did you default on the account 6 years ago? Are you in a DOLA or DOFD state? Are you referencing "open accounts" for the SOL?
I am just curious because Cap1 tried to pull the same thing on me, served me with papers on a debt from 6 years ago. I live in a DOFD state and the SOL for open accounts is 4 years. I used the SOL defense and countersued (still pending).
Just be careful and know your rights. These guys are banking on people being intimidated by the local sheriff serving them papers and not knowing their legal rights.