855-233-8405

Called from local number left vm with this number returned call. Caller claimed to be an attorney representing a bank in Missouri concerning a delinquent debt from some years back went through the whole urgent scheme threatening lawsuit etc. He got really mad when I quoted the Mississippi code concerning the collection of debt and the fact that in Mississippi if the debt has not been rendered judgment on by 3 years from origination it become void. At which point he called me an (explicit) f.... thief and hung up. Also called my elderly parents as well.

Threatening matter I have no knowledge of

Whenever someone tells you that they are a "lawyer" or that they work for a lawyer or law firm, the first question you should ask is what state(s) they are registered in and their BAR number for that/those state(s).  Then go to that state and check them out, contact them directly using the information in the state registration, as these crooks have been known to research real law firm names and attorney names and impersonate them.

It is incumbent upon them under the law to prove that the debt exists and that you owe it, and (this is the important part) that they have the legal right to collect it. You are not obligated under the law to prove that you don’t owe or that it is paid.

Federal law (FDCPA) requires them to send you a letter, email, or text (postmarked in the case of a letter) within 5 days of their first contact that contains their name, physical address, the creditor’s name, and the amount of the alleged debt. Unless they have communicated it to you verbally at the beginning of your conversation. It also must contain the “mini-Miranda” telling you that it is an attempt to collect a debt and that all information will be used for those purposes. The one other important thing that this communication must also have in it is that you have a right to dispute the debt within 30 days of receipt of the letter and if you do so, all collection activity must be stopped until the debt is verified. If and when you get that communication you should immediately send that debt validation letter by certified, return receipt mail.

First, you should make a complaint at this Federal Agency, and while there you should also read up on how debt collection is supposed to work as well as what your rights in this matter are: https://www.consumerfinance.gov/

Also file complaints with the FTC: https://www.ftccomplaintassistant.gov/#crnt&panel1-1

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

I've been getting harassment calls from this number

Did they ever stop. Calling ?

Sara, Marylou posted almost 2 years ago so she's not likely to come back.  Scroll back a bit and read BigA's post.  Good information there that may help  you.