Welcome to the Community, @almarkham. I'd be glad to show you how to stop the link to your bank.
Here's how to disconnect an account in QuickBooks Online:
The following is a brief video to serve as an example:
I recommend the following article for additional insight into this, such as what happens to transactions in For Review when the account is disconnected: Disconnect or delete an account from the Downloaded Transactions page.
I'm sure you'll have the account disconnected and be back to business in no time.
As always, I'm a quick comment away if you should have questions about banking or anything else. Cheering you to continued success.