Records show that you have been assigned a revenue officer. Please call  me asap to avoid collections on your back tax debt. Debra 301 658 6964.    Obviously a scam - I have no tax debt.

This is a very common scam indeed. See this link US Treasury fraud alert,
also this IRS fraud alert:

Quote:...Additionally, it is important for taxpayers to know that the IRS:

Never asks for credit card, debit card or prepaid card information over the telephone. Never insists that taxpayers use a specific payment method to pay tax obligations Never requests immediate payment over the telephone and will not take enforcement action immediately following a phone conversation. Taxpayers usually receive prior notification of IRS enforcement action involving IRS tax liens or levies.
Potential phone scam victims may be told that they owe money that must be paid immediately to the IRS or they are entitled to big refunds. When unsuccessful the first time, sometimes phone scammers call back trying a new strategy. ...

That's what I thought I just received this right now from Debra as well.

Got a text that said, "It's April 18 and records show that you've been assigned a revenue officer. Please call me asap to avoid collections on your back tax debt. Debra 301-658-6964."     But I have no tax debt due.    So I called to see what this is about and talked with Carla Menedez at Tax Law in San Diego, CA. She said they got my name from public records indicating I had a tax debt. And I told her she would not get my cell phone number from court records. I said, I don't owe tax, I always get refunds. She asked twice if I didn't owe back taxes. And both times I answered, no.    She said obviously her records have a mistake and hung up immediately.

Caller had some sort  of accent.  Couldn't place it.  Sounded like she was in a call-center of some kind.  Said she was in San DIego.  Clearly a scam of some sort.

Again just another IRS scammer trying to scare people  into thinking they have a tax liability of some sort.

If you have a tax liability you will receive a written communication from the IRS.  IRS does NOT initiate contacts by phone.  US mail only.

See:  https://www.irs.gov/taxtopics/tc201.html

Ignore and block these callers.