Complaint Review: Penncro Associates Inc For Palisades LLC

I received a letter from Penncro Associates for Palisades LLC regarding a credit card account originally issued in 1998 and charged off in 2000. I don't remember ever having an account with Providian Bank. When I contacted them, they said it would take 30 days for them to investigate. I contacted Penncro, and they informed me they have no information, and to please contact Palisades LLC. I have tried to contact Palisades, but each phone number from the internet on them is incorrect. Also, the first statement said I owed $1140.07 which was sent 3 weeks ago. I received another statement today saying the amount is $2068.18.When I contacted Penncro, the person handling my account said the $900. difference was interest!! I asked what was the interest rate? Any advice out there about what to do next? I find it interesting that Penncro doesn't have a phone number for Palisades. No one has any pertinent information, but they want the money now.
Thanks

Nancy
Mechanicsville, Virginia
U.S.A.