It sounds like you keep on top of your books which is fantastic. The QuickBooks Online bank feed feature can be a real timesaver. It sounds like your sales may have been entered through your bank feeds as deposits into your sales account. They can't be all changed at once; however, they can be done in a few short steps. Let me explain how.
To make changes to categorized transactions, follow these simple steps:
Go to Banking/Transactions.
You'll see a bar of buttons that read For Review, Categorized & Excluded on the Banking tab.
Select Categorized.
Check the boxes of all the transactions you need to correct, and click Undo.
This will put them back into the For review, where you'll categorize them as Sales Receipts.
These articles explain how to categorize and undo transactions in more detail: