Please give us the address you sent that letter to.  And then use the following to make them pay you for their FDCPA infraction.  I have highlighted the relevant sections.

You need to send them a certified, return receipt debt validation, cease and desist calling, or "not me" letter (think of it as the best $6.47 you ever invested).  Also send it first class mail in case no one will sign for it.  Make a notation of that fact at the bottom of the letter.  You also need to report them to the proper agencies to which I have provided links to.  Then you need to go out and get a consumer lawyer to sue them on a contingency basis (no money out of your pocket) and let them pay you for the harassment.  If everyone did these three things, these crooks would be bankrupt and we would all be the richer for it.  Use these web sites to find an attorney in your state that will probably take the case on a contingency basis (no money out of your pocket up front): http://www.consumeradvocates.org/
http://www.consumeradvocates.org/find-an-atto ... tates_value=All

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

As I see it, they are trying to collect a debt that isn't owed, and have ignored a written cease comm letter.

Scam

Received a call from this number just after 8am today but, the caller did not leave a message. I'll update this if they call again and I actually speak to someone.

Called at 9:30 am.   Kept saying hello.  Hung up on me.  Must of known they had wrong person! But I have started answering 800 numbers to stop them, myself.  No call lists dont work.

Received call from this mumbet at 8:25 am pacific time. No message.  I called back. Phone rang 20 times bit no answer. This is the 3rd or 4th time they call.  .