I'm a bit confused. You wanted to buy a thing and amazon ultimately allowed you to do so despite a slight hiccup. Did you not end up getting what you wanted?
I wanted to buy it on installments. That could not happen with Amazon Credit card. Fine. But then it went on to my other credit card and bought the machine itself for the full payment.
Give it back and get a refund for it and buy again with the options/seller you want