Problem
You need to change the customer assigned to a POS invoice.
Solution
In ServiceTitan, find the invoice and go to the Invoice screen.
Click the X button next to the payment and materials to remove them and clear the invoice.
Create a new invoice under the correct customer.
If a customer short pays an invoice and you don't want to worry about the balance, adjust the task amount for the time being equal to the underpayment.
If the invoice was already batched over, unbatch the invoice, add the task amount for the underpayment, then re-batch the invoice.
If the invoice has been exported, create an adjustment invoice for the underpayment.