R W Direct, Inc. Threatening Letters For Collection For amount already paid Farmingdale New York

Purchased the Worx GT 2.0 in July of last Year. There was only supposed to be 3 installments of $33.33 plus shipping. The first installment I made with my credit card for $60.22 which was the first payment of $33.33 plus shipping. Then on Sept. 10th last year, I made the final installment of $66.66. R W Direct continues to send me threatening letters saying that they will turn me over to collections if I do not pay a payment of $33.33. I have sent then all of the information and I still continue to get these threats. I have made contact with the Worx website and they apologized and told me that they would take care of it. Not happening yet. 

I would not EVER purchase something from this company again, and I will let everyone I know know what happened to me and that they keep trying to get money out of you even when you have paid everything in full. They do not provide any proof that I still owe this, I send them proof that I already paid, but they seem to refuse to believe what I am sending them as proof. I do not want to pay an additional $33.33 because not only of the principle of the matter, who is to say that it will be accepted as full payment. Obviously, when you pay in full and they want more, makes you wonder.