Voice Calls Bill / Telecom Complex Invoice Design

We are in the process of redesigning an invoice for one of our telecom clients. We have a reference invoice where we like to take it to. Some analysis is required to determine what elements are required for the new invoice format, which ones are not necessary given our business requirements. We will provide you with the reference invoice and the current invoice and expect you to prepare a sketch with instructions so that our developer can work to make the changes. Ideally you will be familiar with the concept of database and fields, and possibly telecom accounts/billing rates/CDR records.