It's my pleasure to help today, @useroffice5.
To start, we can undo the reconciled transactions. Take note that even small changes can unbalance your accounts. To minimize the impact, you can only unreconciled transactions one at a time.
I also encourage you to consult your accountant if you're unsure. However, if you know what you need to change, here's how to edit and unreconciled the transaction:
Once done, you can disconnect your credit card account connected to online banking.
I've also added these articles that can be handy in the future;
You're welcome to post again here if you need anything else. I'll make sure to get back to you right away. Have a pleasant day.