866-329-4425

Received a letter in the mail stating  I owed a credit card balance of 19,236. but could settle with them for 6,732.00. No name or address of this business only the number to call them  @ 866-329-4425 and a reference number. Stated I should call them before Midnight July 7 before midnight to avoid loss of these negotiated terms.

Scam.

I received the exact  letter today. Scam!

Sending of a post card with that information on it violates federal and state collection laws.  You should take that card to the post office and have them forward it to the postal inspectors, and you should report this to the following 2 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:   https://800notes.com/faq/attorney-general

I just received the letter I owed $19,236 will reduce this amount to $6,732, benefit expire on Aug. 18, 2017.
So I call the number 866-329-4425, to ask them where are they locate. They told me their company at Golden Colorado.  A lady just insists me what do I need for help, and she asks about the case number in my letter.  But I said nothing,  I dont need any help.  So I hang up the phone.

There was no company name and address on the letter?  I would suggest that you take that letter and the envelope it came in to the post office and have them forward it to the postal inspectors.