Actually, no.  Real process servers do not call and give you a heads up - that would give you the opportunity to make sure you weren't available when they come to visit.  If you were going to be sued in the first place, you'd have received lots of letters asking you to pay the debt.  You wouldn't hear about this via a scammy, threatening phone call (which is illegal).
https://www.consumer.ftc.gov/articles/0258-fake-debt-collectors