First off, there is already a chanspy feature code, 555 that allows you to listen in on calls. If you want the above customization, the content goes entirely in the file extensions_custom.conf and if you’re unfamiliar with editing conf files in FreePBX, you probably want to use the Config Edit module: https://wiki.freepbx.org/display/FPG/Configuration+File+Editor+User+Guide
Once in place, do an ‘apply config’ in the GUI, and then you will be able to dial extension numbers with a 555 556 prifix to listen in.
or maybe I’m doing something wrong. i have an extension 1009 that I want to listen to.
i’ve tried dialing *5551009 and also 5551009 and it wont allow me to.