Billing multiple Field Service Assets under one customer.

Good morning. I work for an HVAC contractor and we are currently using NS and the Field Service. Recently we have encountered some customers with multiple field service assets (job sites) that each will need a planned maintenance project unfortunately the customer does not want an invoice for each FSA they want one invoice and one sales order for all 6 locations. How can I do this where I can have the project and scope of work for each location but then tie them all together with one sales order and one combined invoice. I really