Hi ccgraphic-design,
You've come to the right place to ask about adding the client information you mentioned to your customer's invoice. Let me guide you through the steps..
To don one invoice transaction per customer and click on the Edit customer info hyperlink. You will see a side window on the right where you can add the customer's phone number, edit the name, and company name. The Company name is in the Additional info section.
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Please don't hesitate to reach back out if you have other questions about your invoices.