Finance Charges Customers

I have a unique situation that I need to address.  

I have a customer that I invoice for 3 different scenerios.  

The customer rents 2 properties from us, so I decided to add 2 more customers, with the invoices split into 3 different customers.   1 customer for each property, and then the 3rd customer is the original for any other type of invoices. 

This customer is having an ongoing dispute with rent and tmi the 2 properties and he has also stopped paying some of the other invoices for the original customer invoices. They have either short paid invoices and or not paid some others. 

In the past I assessed Finance Charges through Quickbooks Desktop Pro Canada. 

Now I have changed all the invoices for the 2 properties, to the appropriate Customer for each property. This is so I can produce separate statements for Property Managers.   

However, how do I reverse the FC and re-assign the finance charges for all the short payments they made on the old invoices. 

I haven't tried to reverse or credit the FC yet, as I wanted to see if there is a correct way to do it so that the FC can compound on the invoices.