It's good to see you here in the Community today, @hanescpa.
I'd be happy to get you pointed in the right direction so that you can delete the incorrect Merchant payment on your QuickBooks Desktop.
I appreciate you trying the steps given above. However, if your transactions were deposited and recorded already, you'll need to reach out to our Merchant Services Department. This team is the best resource for such concern as they're able to pull up your transactions securely and help you with the deletion process.
You can reach them through the contact information found in this link: Merchant Services Department.
This should get you on the right track, @hanescpa.
Don't hesitate to let me know if you have any other questions with this concern or anything about QuickBooks. I'm always here to help. Have a prosperous day!