They say they are a debt collector of a debt from 1998 --- which i find hard to believe.....  i can assure you i do not recall what i was doing 16 years ago.  Plus this has not shown on my credit report...  so hummmmmmmm  not for sure what this is but i dont' find it legite.

I can assure you, they're NOT legit. They're most likely just scammers. There's a chance that they're collectors for a Junk debt buyer. Either way, a 16 year old debt is past the Statute of Limitations in regards to debt in every state. Do NOT pay a dime. Doing so may revalidate the debt. Which is exactly what the cretins calling you want to happen.
Know your rights under the FDCPA. It's easy. Just Google it.
Be Safe. Be Aware.
Gunnar

Well it is 2017 and the number is active again. They call but leave no message.