When a credit card transaction is tagged as fraud, a new credit card NUMBER is issued, but the ACCOUNT doesn't change: one should be able to change that number when editing the account!!
I'm assuming you are talking about a credit card that you are downloading transactions into. Am I correct?
If that is what you are talking about, you most definitely can update your credit card number in the current credit card account in Quicken.
Your account will now be linked to the new credit card number. Then in the Account Register:
At this point your account register balance and the Online Balance should be in agreement and you have completed the task.
Let me know if you have any questions.