If the Periodic Billing batch has not yet run, the charges can be viewed and edited by going to Periodic Billing > Batches.
If the Periodic Billing batch has already passed the "Next Run Date," the transactions will not be available in Periodic Billing, and instead they are available under Transactions > Current Transactions.
If the customer does not know their "Next Run Date" and the batch has been run, you can verify the "Next Run Date" by l going to Periodic Billing > Customer Maintenance and looking up the user in question.