Webhooks integrations into custom Java/SQL based program

I have a custom program thats already built and web based which utilizes java and sql, its a live system and is very complicated, for now i need just a basic issue troubleshooted, this system connects to a voip system that has been integrated in the past to load new calls on the system as they come in, something went wrong and it stopped working. the integration uses JSON. once the issue is fixed and active i'd like to utilize more features of the integration like connect the voip system to send out an email each time there is a call and each time there is a missed call that the email says "Missed" this way every call is handled right away. you need an extensive knowledge of Java and SQL in order to complete this project so please dont waste my time only apply if you are confident this is something you know. also I require a NDA signed before any work is completed and all work must be done via remote access either logmein or teamviewer