Capped Packages Billing Question


I have an interesting question that arose in a financial discussion this morning which could have a major impact on billing our clients.

Our capped internet package clients :

If a client wishes to downgrade or upgrade their capped package to a different package mid month how will this affect the billing part thereof.

For example :

Client A is on a 100GB Capped package, Client A wishes to downgrade to a 75GB Capped package on the 16th of the month.

The 100GB Capped package is sold at a monthly price of 599.00 and the 75GB Capped package is sold at 499.00 per month.

How will the end of month billed calculation be calculated?

Many Thanks!!