Yes, you can. We normally automatically match expenses to bank transactions. It happens we make a mistake. In this case, you can manually link it to a different transaction.
How? Open the "Link Payment' menu in the 'Edit/Add Expense' screen and choose the transaction.
In the lower part of the screen, click on 'Link payment' and select the right transaction from the list. It's done.
Still in doubt? No problem, we are available in the chat & email.