Hello, It seems as though my question has been asked a number of times and that no one has ever found a real solution (or I couldn't find it!) - searching the forums has returned the following threads: Blocking Extension to Extension calls Prevent users groups calling other user groups Internal Call Blocking I have 3 groups, A, B and C. I need to prevent groups A and B from calling each other. However, I need groups A and B to be able to reach group C. Extensions in group A have format 51XX. Extensions in group B have format 52XX. Extensions in group C have format 53XX. I created the following outbound rule to limit group A from calling group B Code: Calls to numbers starting with prefix: 52 Calls to numbers with a length of: 4 Calls from extension groups: Group A Route: Block It didn't work. I know I can limit how an extension receives calls by creating an exception under the "Forwarding Rules" tab of the extension's settings - but this is far from ideal. This could probably be achieved using device dialplans (as has been suggested in some of the other threads) but does not solve my problem if a user is using the 3CX clients. So... 1 - Is it possible to prevent one group from calling another? 2 - Is it possible to allow extension 5111 to only be able to call extension 5333? I'm using v15.5 on Debian. Thanks for any help!