How to add department in 3cx free (10 user) v:20

I want to put outbound rule so that only one user can use particular sip trunk for outgoing call. How to add department in 3cx free (10 user) v:20. as the outgoing rule only based on department & where is the capability to add additional department in 3cx-smb(free) version:20. also call from extension is gray out, is it paid feature? the main thing is i want to control 911 calling from desk phones only. i do not want any mobile user call 911 number.
thanks