I made an invoice but I billed the wrong customer? I can't seem to change it?

Let's work together and send an invoice to the correct customer, @trudyjohnson18 .

To begin with, you can contact the customer who received the invoice to clarify that it wasn’t intended for them. Inform them that they don’t need to make any payment. Then, you can delete the existing invoice, create a new one, and send it to the correct customer. 

1. In the Sales menu, click the All Sales tab. 
2. Choose the invoice you want to delete. 
3. From the Action column, select the dropdown option. 
4. Choose Delete. 
5. Select Delete once prompted with a warning message.

Moreover, have you encountered any errors when changing the customer?

If you haven't received any errors, let's see if the problem is caused by excessive browser data. It could be affecting the performance of QBO, leading to unusual behavior in the system. To confirm, please open your QBO account using a private browsing window.

Kindly refer to the keyboard shortcut keys below to proceed:

• Google Chrome: Ctrl + Shift + N
• Mozilla Firefox: Ctrl + Shift + P
• Microsoft Edge: Ctrl + Shift + P
• Safari: Command + Shift + N

After opening QBO in a private window, let them try to edit the transaction. If the update is successful, clear your regular browser's cache and cookies. You can also utilize other supported browsers.

I'll include this article to help you void or have a refund to your customer payments in QBO: Void or refund customer payments in QuickBooks Online. 

Let us know if you have further questions about managing your invoices. We'll be right here to help you at any time.