Extortionists pretending to be debt collectors.  Don't try to reason with them, they are simply illiterate scum.  They don't care about laws.  Stop answering and get a call blocker.  Also make sure you report them to the following two agencies:

Read up on your rights here and also make a complaint at this government site:  http://www.consumerfinance.gov/

Also file a complaint with your State Attorney General's office.
List of State AG’s offices:   http://800notes.com/faq/attorney-general

Said I have a case pending and I or my attorney need to contact them.