If selected, then prefix the phrase "Purchase Requested" to the method of Payment in message to back-end. If no Payment Method is selected, then just include "Purchase Requested." Message to back-end should be one of the following depending on whether "Method of Credit" is specified or not:
Purchase of Bill is Requested
Purchase Bill and Credit Our Account xxxxxxxxx with the proceeds
Purchase Bill and remit a Manager's Check for the proceeds
Purchase Bill and remit a Demand Draft for the proceeds