It is bit tricky to handle a partial cancellation, because the payment providers, including Klarna do only allow to cancel the remaining amount.
As at now, clear way to handle it is as follows:
- Do NOT change the order.
- Make a full charge of the order.
- Process a return order, for the items that could not be delivered.
Customer service should explain that to the end customer, “the amount for the items that we cannot deliver will be refunded”. So customer is not confused.
It will be very easy to do this using Litium Connect APIs