The behavior depends on several factors:
- the mode of Billing: Prepaid or Postpaid
- when the plan change is made
1. If the application plan is changed on the same day as is it was created, and so it has never been invoiced before, the fixed costs for the old plan are included to the invoice, and are discounted with a 'Refund' line item. The fixed costs for the old plan are also added to the invoice.
Example.