When it comes to managing customer's debits, nothing is set in stone.
Your customers may request to change their next debit due to a variety of reasons. For example, Jack may be going away for a one-month vacation and therefore would like to bring forward his next debit date a couple of days earlier.
On the other hand, you may be the one who wants to change the customer's debit. For example, you may want to give Joanne a birthday discount as part of your customer reward program and therefore change the amount for an upcoming debit.
Here are several things you can do, depending on your user role.