Add fee to paid-for order and invoice balance

What would be the best way to add an additional fee to an already paid-for order and allow the customer to pay for the remaining balance?

My scenario is the following:

1. User purchases a product and pays for it.
2. User realizes he/she made a mistake and contacts the store to modify the order.
3. The items bought do not change, but I need to charge an extra fee, which I add to the order manually.
4. I need the customer to pay for the remaining balance.

And here is what I expected to work, but doesn’t quite:

1. After my client contacts me I change the order status from “completed” to “on hold”.
2. I edit the order and add the fee manually.
3. I recalculate the totals.
4. I change the order status from “on hold” to “payment pending”.

However, when I do this and the client logs to their account and click on “pay” they are charged the full amount of the order, not just the remaining balance. It’s as if the system did not recognize the first payment.

Any ideas?

• This topic was modified 3 years, 10 months ago by hoiol. Reason: formating