When you set elastix, you hope the specific extension just can call the other internal extension, and it cannot call out through any trunks, you can refer to the below method:
1. please go to the extension which you want to set, and change the context as no-outbound:
2. please go to PBX->Tools->Asterisk File Editor, and find the file extensions_custom.conf and then open it.
3. please input the related dialing rule in the end.
here if your extenson is like this:801,802, and so on, X represents the number 0-9, and one X represents one digit.
If your extension is 7001, you can set 7XXX here.