Invoices for Billing

To make customized Invoices to bill clients and Credit Notes for agents. We make the Template images internally with LibreOffice, to be used as background for the spreadsheets who will be filled out on the internet. These background images allow every client to have his own, personal template, with his name, logo, etc. These spreadsheets with background images and calculations, must be changed to pdf without loosing anything, before they are stored on our server. There they will be filled out and send by email to their final destination, as invoices and Credit Notes. The client never sees the spreadsheet, he only sees the background image ! ***** Requirements: 1) LO Calc or similar spreadsheets, with interchangeable background images of Invoices and Credit Notes. 2) Software (open source or homemade) to change the ods files to pdf, without loosing calculations ! 3) Asterisk CEL (not CRM !) must be used, to fill Cells on spreadsheet. ***** This is not a standard project and not for beginners ! Very good knowledge of Billing software and Asterisk PBX is needed. Good communications are necessary, to ask questions and give answers ! No Windows -- Linux only ! See, read and understand the attachment for more info and steps to follow.