Thanks for getting back in here, @Andrew93.

Let me provide additional steps on how to delete customer payment in QuickBooks Desktop. 

Here's how:

1. Open the Customer payment window.
2. On the top toolbar, click the delete button.
3. If you get a warning saying delete if from the deposit first, you need to delete the payment from the deposit.
4. Click Save and Close.

Also, to view the deposit payment for the invoice, you can follow these steps:

1. Open the affected invoice.
2. There are two tabs on the right panel of the Create Invoices window.
3.  Go to the Transaction tab.
4. Under RELATED TRANSACTIONS, it will show the deposit you use as the payment.
5. Click the deposit transaction. It will open the Make Deposits window.
6. Click Edit at the top menu, and select Delete Deposit (Ctrl + D).
7. Click OK to confirm the action.

If you're still unable to delete the payment, I suggest contacting our support team. They have the tools to check your account in a safe environment. This way, they can also further assist you to delete customer payments.

You'll want to personalize email templates. Feel free to check out this article for more details: Create custom email templates in QuickBooks Desktop.

Let me know if you have other queries aside from deleting customer payments. I'll be happy to help you. Have a wonderful day.