Keep extensions from calling other extensions?

In a multi-site system is there a way to keep a group of extensions from calling other extensions on the same system? I thought this might be COS but it doesn’t seem to be the answer. Thanks

Someone more knowledgable might be able to weigh in, but I would look at the Custom Contexts module.

I’ve used this before to restrict certain extensions from placing calls over a trunk.

Although technically possible with custom-contexts, you will find your work seriously cut out for you. You will need to build separate contexts for each of your multi-sites and put all those multi-site extensions in the right context, you will have to do the same with your voicemail contexts. Then you will have to build similar inbound routes and outbound routes to suit in similar custom-contexts, the list goes on . . . . .

In other words, FreePBX is JUST NOT untended for multi-site use, Just build lots of FreePBI under a decent Virtual environment and save yourself many, many hours of frustration and failure.

(I don’t know of anybody who has successfully done that multi-site thingy here.)