First you need to unapply the credit amount from the applied payment, make sure to attach the reference batch you posted in. Go into the receipt dashboard and select Post (Expert Mode). Select the Encounter the payment was applied to.

Then make a negative patient payment for the amount of the credit.

This will create your Escrow to apply to the correct charge. 

Next go to the receipt dashboard and select post. You will see the escrow amount in Yellow with the charge that has a patient balance. You may have to use Post (Expert) if the client doesn't have a balance on the encounter.

You will select the check box and the escrow amount goes away. Then Save.