What can they do to me regarding credit card debit and they filed a lawsuit
The police came out to serve me the notice today
The bill is close to 15 years old
What can they do to me

If the bill is 15 years old then the statue of limitations would come into
Play

Does this have anything to do with your partners debt from your other posts ?

But something is wrong, if this is 15 years old, then they can't sue you for it, ( unless it is some government taxes or student loans)
But for a credit card, if it is over I think 3 years old they can't even sue you.

Best to hire an attorney to represent you, but you respond by saying this is not a valid debt, asking them to verify the debt and that even if it was a valid debt it is post the SOL and the case should be droped.

If it goes to trial your defense is that the case is past the SOL.