Here's a question based on our current headache: our bank switched processors, and now when we try to do AMEX refunds our gateway (Payflow Pro) returns an error

Here's a question based on our current headache: our bank switched processors, and now when we try to do AMEX refunds our gateway (Payflow Pro) returns an error. The old transaction tokens don't work with the new processor. How do you guys handle this situation?