Tell them not to call you again. If they are reporting your account number as a Court index number they are committing fraud.
So do nothing, let them sue, prove it's past the SOL.
Equifax has nothing to do with a lawsuit over this. That's a credit report, totally different from a collection matter.
If you tell the collection agency not to call and they do call, report it to your State Office which handles these things - usually the Attorney General.
EDIT: Please stop asking the same question - asked and answered:
https://www.askmehelpdesk.com/other-...ml#post3466514