This is a version of the you-have-committed-a-crime extortion scam and you are being...
1. summoned/investigated/charged/whatever with fraud/embezzlement/passing_bad_checks/whatever or
2. served with a court_summons/arrest_warrant/bench_warrant/whatever or
3. located in preparation to_being_served/for_a_lawsuit/to_be_arrested/whatever or
4. sued for cable TV usage that you've been stealing for years or
5. whatever stupid crap reasons they will think up next.

And you have to...
1. call back with your case number or
2. confirm your address/birthdate/SSN/whatever so you can be served or your papers processed or
3. pay $895 now to avoid paying $5,000 in court or
4. whatever stupid crap reasons they will think up next.

Beware extortion scams come in many flavors and they constantly evolve to stay one step ahead of the law.
The FBI warns about payday loan extortion scams here http://www.fbi.gov/news/pressrel/press-releases/paydayloanscam_120710
The BBB has issued several alerts on this scam, just google "bbb.org alert phony debt collector"
Never do what they tell you to do but report them to the Internet Crime Complaint Center http://www.ic3.gov/complaint/default.aspx , the Federal Communications Commission http://esupport.fcc.gov/complaints.htm , the Federal Trade Commission https://www.ftccomplaintassistant.gov/ and your state AG, as appropriate.

I just checked National Check Recovery Services website. What a joke. They don?t even have a physical address listed. I guess they?re afraid Brad Shelton will show up and serve them papers (lol).

National Check Recovery Services has a website that looks like it was made by a Highschool kid. It is hosted by JUSTHOST.COM  - They pay $3.75 a month for it. TOTAL SCAM!!!!!!!!!!!!

It's now been six days since Brad Shelton said he's coming to my house with papers for me to sign. TOTAL SCAM!.  He's in hiding somewhere in upstate New York trying to scare people into calling him back, so he can convenience them that they owe money. If he calls don't take him seriously. He's not going to anyone's house.....

I received a call from Brad Shelton telling me he's coming to my house at 2pm to serve me papers and to have my ID ready. I's now 2:30 and no sign of him (lol). I guess it takes to to travel from Alabama. (see post from angelprevos). I live in California.

I just recieved a message from this Brad Shelton, using a very threatening tone, and saying the same thing as these other comments, will be at my door, will be suing me,  I tried calling back, but I dont get to speak to this Brad Shelton, same thing as other people reporting this.   A previous message left stating that he was a detective with the police department in TX? the worst part is that I had to reply the message 4 times in order to understand him, language was foreign, and stated he had my name and social security number and that I will be summons if I dont return their call.   I google the number and it shows no company name.   Person calling me does not leave the name of the company. and when I google the number it shows these messages from others that have recieved the same messages as I me.

I am also getting thetening calls from this brad shelton, no idea what they are talking about  callednuber he left 888-507-7343  they at first said thy knew nothing about him, then claimed he was a courier who was deliverig  court summons,   told them if this man showed up onmy doorstep would press charges against him and them.   they claimed i owedsome copany Ive never heard of, then said oh if you pay us $800 we ill drop the claim.     Im in Alabama

No! Collectors cannot serve anyone papers to appear in court. And no! Collectors have no authority to call you all the time. Collectors are bottom feeders who exploit and extort us for our money. The only effective way to have them stopped is to call 855.672.1988. The help you receive is free and more over the results are fast.

Doing some more research: This is from another post. Apprarently these people use different names when calling. If you are in Texas, this will be helpful:

Texas replies to Surprised
23 Jan 2011
I won a judgement against these People.  They do not show up with papers as promised and mis quote the debt.  If you get calls from them google FDCPA law firms in your area and try to hire one.  Most of them don't charge a fee, they get their money from the recovery.  Only way to get these bottom feeders to stop is hurt them in pocket book. A special note if you are in Texas.  Texas financial code 392.101 requires debt collectors to have a $10,000 surety bond on file with the Secretary of state of Texas to legally collect.  Go to the website. You will find a link there where you can check if they do. If They don't DEFINITELY Hire an FDCPA lawyer.

I have been receving calls from an unknown number. The person identifies himself as Brad Shelton and he is calling to let me know he will be serving me a "legal document". He is supposed to be delivering the document between 10-2 today. He said he will try my home first and then my place of employment. He does not leave a company name or anything.  He left this number to call the claimant 888-507-7343. I called the number and it is for National Check Recovery Services. The rep that answered said there was open loan under my ssn and said I owed the money. I was not familiar with the company and told her so. I also told her if I am being served some type of legal document that they could call my attorney. She refused and said the attorney could call them. I immediately knew something was strange about this so I started researching. There are numerous stories online about this National Check Recovery place using the same story. Some person will be serving you papers at your house or place of employment. This Brad person is supposed to be at my house today by 2pm. His last message said if I was not available the documents would be surrendered as refusal to sign. I have already contacted my lawyer, the state attorney and filed a complaint online with the FTC. I will be saving every message and recording every call made to catch these frauds!