Dynamic Recovery Solutions intimidating, rude, wouldn't let me talk, put words into my mouth Internet

Received a message on my cell phone on 11/9 regarding a debt.  Called back to inquire about the debt, since I just refinanced my mortgage and there are no outstanding debts on my credit report.  When I called back, I was told that the last activity on the account was in 1996.  They were not able to give me the original account holder, balance, or account information.  The man I spoke with told me that a letter was sent on 10/14, which I never received.  He told me they could not resend it or e-mail it to me.  A 'settlement' of $600 on a $1645 balance was offered.  When I informed him that I needed to do some more research into the matter before giving him my bank account information, he told me that the account would be reassessed at 5:30 tonight and that I would have to pay the full amount after that time.  I expressed concern about the last minute nature of this matter, that I had to agree at that very moment, and he said that I was stalling and trying to get away with not paying my debts.  He said he would mark the file as refusal to pay, and I insisted that was not the case.  He said he was tired of me wasting his time and stalling.  What kind of company is this?  The pressure to pay at that moment and unwillingness to allow me to do any research made me question their tactics.  SOmehow, they have a high rating with the BBB?