Help, I've linked 2 bank accounts to existing accounts in QB but done it the wrong way round. How can I put this right?

Thanks for reaching out to the Community forum, @carolinejanesali.

We can try reconnecting again to download the correct transactions. But before doing so, you'll need to exclude the transactions that were downloaded to the wrong account. Let me show you how:

1. In the left menu, click Banking or Transactions page. 
2. Go to the Banking tab and select the bank account.
3. Tap the For Review tab. 
4. Select multiple transactions that need to be excluded.
5. Hit the Exclude button. 

Once it's excluded, it'll now be transferred to the Excluded tab in which you have the option to delete it. 

You may want to visit this article to learn more about excluding transactions: Exclude a bank transaction you downloaded into QuickBooks Online.

Once done, you can now reconnect the right account and download your banking transactions. This will get you back on track.

To help you manage your bank transactions and reconciling your account in QuickBooks, you can visit this link: Banking. 

Please know that I'm only a few clicks away if you need anything else. Cheering you to continued success. Have a great day.