Chargent add’s a Workflow Rule called "Payment Request Email". This Workflow Rule will trigger when the Send Payment Request equals True (and) the Payment Request Status is not equal to Paid.
This will send a Salesforce email template called Payment Request Email. The email template can be modified to add additional merge fields or update the wording to match your companies tone. You can also modify the Workflow Rule to send a different Salesforce Email Template that you create.