partial payment with points

Hi.
I made a partial payment with points, and I have the following problem:

Imagine a Buyer purchases goods for € 2, and the points he's only got 1. The choice of payment he selects "Pay with points". After he confirmed the purchase order status becomes "reserved". Where in Your understanding, he chooses a different payment option if the order is "reserved"? I never see that option another option of payment of the order is not found. You lead people astray? Please show a demo.

Recall that the product in a single copy. In stock product all one. And after placing the order, shows that the cart is empty. It was the latest instance of the product