I'll walk you through how you sync your replacement credit card to your QuickBooks Online (QBO) company.
You'll have to disconnect the original credit card account first.
Follow these steps:
Click the Transactions tab.
Select the correct credit card account in question.
Press the Edit (pencil) icon, then choose Edit account info.
On the pop-up window that appears, tick the Disconnect this account on save box.
Hit Save and Close.
You can connect your new credit card account at this point, and you have two options. You can either use a new one from your Chart of Accounts or continue to use what you have before.
If you want to set up a parent credit card account with sub-accounts in QBO, take a look at this article: About bank or credit card subaccount setup. It has the steps on how you can create this type of setup in QBO.
In case you need further assistance, don't hesitate to post a comment below. I'll get back to you as soon as I can.