Mass Street Group Loan

Earlier this year, I had a financial hardship and started researching some payday loans. I submitted an application through Money Mutual, but decided not to take a any of the offeres that were made. Just seemed like I would get myself into trouble.
The next day, I had a deposit in my account from Mass Street Group for $200. They were not on the list of lenders that I was "approved" through, and I certainly did not give them authorization to deposit money into my account.
I attempted to contact them at the number listed on an account summary they sent me, but my call was never answered. Looking back, I realize I should have contacted my bank to have them send the money back, but it's too late for that now.
I attempted to initiate a repayment, as instructed through an e-mail they sent me. They said to repay the loan in full, I had to fill out a form and fax it to them at least three full business days before the loan was due, or I would be charged a refinance fee. I submitted the payoff request five days before the loan was due, and they did not take the money out as I requested. Instead, they just took out the refinance fee of $60. I tried repeatedly to fax and call them to initiate repayment, but they never took the money.
The first $60 was taken out of my account on 12/9/11. Despite my attempts to repay the loan, $60 was continually taken out of my account every two weeks until I closed my account in July. I attempted to repay on three separate occasions.
After I closed my account, I got an e-mail stating that my Mass Street Group account had been sent to "National Credit Adjustors." And yes, they spelled it adjustors incorrectly with an "o" instead of an "e."
I have now received two threatening voicemails, both saying that legal action will be taken against me. Today was the last straw, as they called my work on my day off and spoke with my manager. (My manager called me and informed me of this).
I live in Iowa, and I know Mass Street Group is not a licensed payday lender in my state. I have paid well over what I owed on the principal balance. I understand that they owe me money, but in all honesty, I just want them to leave me alone.
I understand it may be possible to inform them in writing that I know the loan they gave me (the UNAUTHORIZED loan, at that) is illegal, but I have heard of other people not having any luck with this particular lender in doing that.
Here is what little information I have on Mass Street Group:
Phone: 1-877-781-4330 (although this number is NEVER answered)
Fax: 1-800-708-4351
E-mail: [email]massinfo@cwbservices.net[/email]
I cannot find a physical address for them, which is not a surprise. Should I possibly try to fax or e-mail them? Or should I attempt to deal with the debt collector? (Although I question the validity of the collection agency.)
I'm fully aware that I've been scammed. As I said, my primary concern is to get them to leave me alone, and not get whatever money may be owed to me. Funny that I decided to not take out a loan through Money Mutual because I knew it would only cause me problems, but somehow I am STILL in this situation. :mad:
Thanks in advance for any help.