Scenarios:
1)
Authorization was processed with billing descriptor 'A'
We then changed the billing descriptor to 'B'
Will capture for that authorization works?
2)
Capture was processed with billing descriptor 'B'
We then changed the billing descriptor to 'C'
Will refund for that capture works?
A change in the billing descriptor should not impact your ability to capture or refund. Having said that, I'm a bit mistified why you would want to change the billing descriptor on each transaction. The billing descriptor is what appears on the customer's bank statement and is intended to help the customer recognize the transaction and (among other things) reduce the chance the customer will enter a chargeback, because they don't recognize the change. Also, while I am not an expert in card network regulations, I don't believe you are allowed to change the descriptor on each transaction in a stream, as you describe. In fact, on the eComm platform, you cannot change the billing descriptor on a credit (refund) transaction. The customBilling element is not part of that transaction structure.
Tom