Yes. You can reopen the invoice and modify the services in it.
Reopen the invoice and then do the following to edit it:
Delete the payment methods added for the services by clicking the red cross icon against each payment method (if more than one).
Delete the service you want to remove from the invoice by clicking the red cross icon against it.
To add a service, click the Service tab, select the service, therapist, and then click Add Service.
Repeat for each service you want to add to the invoice.