National payday loan- TPS recoveries

I had a payday loan through National Payday loan and after a lot of helpful info on this site I sent them the letter that stated in the state of MN their loan is not legal here and internet lending sites are still bound by MN laws. They sent the file to TPS Recoveries and the man that called me from there is very rude. They have been calling my work at least once a day for about the last month, this morning I called it back again and he was once again very rude. He told me to pay my bill and that I would have to request in writing for my work number to be taken off but when I asked him for an address or fax number he told me no and hung up on me. I called back and he then told me to stop harassing him. How do I go about getting this company to leave me alone without any other contact info aside from a phone number which is 651-217-1251?? I don't owe them any more money and they can't keep calling my work! Without an address I don't even know how to go about filing any complaints against them. Please help!