Collection letter on unknown debt

What is the name of your state?MA
On August 10, I received a letter from a collection agency stating I owed their client company $160.00. I immediately sent a response letter to the collection agent informing her that I had never heard of said company and until I received copies of invoices and bills for monies owed, I considered the matter under dispute and would not pay on it. Never received any response from collection agent nor the documentation I requested.
Today, Sept 22, I received another collection letter (from a different agent) stating that they've "tried to reach me to no avail" and "previous correspondence has also been ignored", and I have 15 days to pay this $160 or they will "take any and all action our client feels necessary to protect their interests". These people have never left any message on my answering machine, and I've already sent them a written response to their previous letter!
I called the collection agency but got nowhere (I was told that agent wasn't there). However the woman I spoke with did see a notation in the computer that my letter had been received and I was disputing the charge. What are my rights here??? I've worked so hard to keep my credit rating good, I don't want these schmucks to mess it up! HELP!!! I also e-mailed the client company directly regarding this, and asked them for the documentation. I also asked why they would turn an account over to collections without ever contacting me directly.
What else can I do to end this drama?????????????

[cmorris]

Send another letter, certified mail return receipt requested, requesting validation. Apparently, this CA does not have it or would have sent it to you, per your previous request. Proper validation is NOT a computer printout. Include a phrase to only contact you by mail.

By sending this letter CMRRR and only doing things in writing, you create a paper trail. Refer to the Fair Debt Collection Practices Act (available at the FTC website) to let the CA know that YOU know your rights.

The CA does not have to provide validation, but they cannot continue collection activity (including reporting this as verified to your credit reports, unless stating it's disputed). They can, however, sell this to another CA. This will start the CMRRR letters all over again. But they may just forget about it.

OK, I went and did that today**************.....Thanks for the information!!