Customer Account Type should work with the Default Rules. If you set the Rules to Credit, then you will only be able to Settle a Ticket when the Account has sufficient funds to cover the “Charged” amount that you enter into the Payment Screen.
Do you have a Payment Processor defined on the Customer Account Payment Type? You don’t need a Processor, but it can be used to limit payment among other things.
What does your Customer Account Transaction Type look like?
