Valentine & Kebartas threats, Lawrence Massachusetts

I received a call from Valentine & Kebartas on the 24th of February stating that I have a past due account with Dell and that I needed to pay $991 today, and that they would set me up for payment arrangements for the rest of it. So, I asked what the amount was, and she said $4,464.00. I of course was surprised, because I only have one account with Dell and that one has been paid off for who knows how long. I proceeded to tell her that I don't owe them that amount, I was not in the mood to deal with this and I asked If I could call her back and she said NO, they had to have an arrangement today unless my account was going to go to Litigation, and they would take my house, and garnish my wages, and on top of that she said that I should get a loan so that I could pay this balance in full. I told her I will make one payment of half of the $991, so I gave her my bank information and I received a letter stating that a payment arrangement had been set up.

So, I received a call on Wednesday, stating that my payment had came back - which is not true (because I called my bank and nothing had come through), so I proceeded to tell this oh most intelligent representative that that should not have happened because the money was there (I made sure that it was). I told her that I don't feel that I should have to pay for things that I did not purchase, and she said, so are you refusing to pay; I said no, I am requesting a validity of the debt and she said, I don't understand (like what is there not too understand) and she said you need to call back before 2:00pm today unless I will forward this as a refusal to pay.

So, I came home typed up a letter, requesting validity of the debt, and explaining to them that I only have one account with Dell, so I call her back after I send the fax, and she is still saying, i don't know what you want me to do, and then she puts me on hold, goes to talk to her supervisor, and says that I need to Western Union money to them, and that they will call me back in two days to go over the purchases, and at that time there will be no payment arrangements made I either need to pay the full amount or they will take my house.
What kind of collection tactics are these - I have never ever heard of anything like this.

Disgruntled
Smithsburg, Maryland
U.S.A.