If you are reselling Hosted Lync with outbound voice services (Plus and Enterprise Plus licences) then you will need to bill call usage separately. This article helps get you started.
Lync service licences are billed through the Gradwell Cloud Associate platform. This will be done automatically. If you have setup a payment gateway for customers to use they can access this to make payments.
These costs are likely to be static month to month, unless your customer has upgraded or downgraded the service.
Call charges are dynamic and unfortunately the Cloud Associate platform does not have a billing engine for voice calls. Therefore we utilise our VoIP platform to calculate call charges.
You can download the invoice data from your VoIP control panel using the End-user Billing section.
There are guides to invoicing VoIP customers in the Partner Training Portal within the Administration section. There is also example exported invoicing data which you can use to input into your systems in advance of billing your first customer to ensure that you can input the data into your accounting systems.
Therefore you will need to create invoices for call charges manually. If you use credit limits on customer account in the the VoIP system you will also need to ensure you record payments for call charges as they're received.