Upgrading System and Monitoring Plan

I just purchased the Gen 3 base station and sensors to upgrade my existing original system.  I have the interactive monitoring plan now, and want to monitor the new upgraded system, but not the old one which I will soon be replacing.

How do I do this? I don't want to be billed for 2 systems for interactive monitoring.  Just the new one once I receive it.  Is it straightforward to remove the old system from monitoring and add the new one?