Welcome aboard to the QuickBooks Community, Neetha M S.
I can show you how to unmatched a transaction linked to an invoice in QuickBooks Online.
Here's how:
1. On the left navigation bar, click Banking.
2. Go to the Banking tab.
3. Click the drop-down arrow next to Bank and Credit Cards.
4. Select your bank.
5. Go to the In QuickBooks tab.
6. Look for the transaction and click the Undo option below the Action column.
The article below will help you perform the process:
Unmatch and delete downloaded transactions
If you need more assistance with separating the transaction to the invoices. please to let me know. I'll be around for you.