*72 can "call forward" anybody's extension!

You are correct. However, it's a standard feature code and if you go to feature codes in the pbx web gui you can disable this option, it is the very first line there. Just disable this option and submit the changes and click the orange update bar

I found this a while back (not sure if it still works but it could be edited to work if it doesn't) Thanks to user Dickson for contributing...

Original article can be found here:
http://www.trixbox.org/forums/trixbox-forums/help/activate-call-f...

Need to try the following by setting as a Voicemail locator option VmX or just setting a hidden option in the IVR.

Drop the code below into your extension_custom.conf file
Point an IVR prompt to "CUSTOM" and enter a destination of
custom-cf-on,s,1 (to enable)
custom-cf-off,s,1 (to disable)
The code will ask for the users voicemail password (that corresponds with the extension they want to call forward to) as verification and applies the callforwarding.

[custom-cf-on]
exten => s,1,Answer
exten => s,n,Wait(1)
exten => s,n,Playback(call-fwd-unconditional)
exten => s,n,Playback(please-enter-your&extension)
exten => s,n,Read(fromext,then-press-pound,,,,)
exten => s,n,Wait(1)
exten => s,n,VMAuthenticate(${fromext})
exten => s,n(startread),Playback(ent-target-attendant)
exten => s,n,Read(toext,then-press-pound,,,,)
exten => s,n,GotoIf($["foo${toext}"="foo"]?startread)
exten => s,n,Wait(1)
exten => s,n,Set(DB(CF/${fromext})=${toext})
exten => s,n,Playback(call-fwd-unconditional&for&extension)
exten => s,n,SayDigits(${fromext})
exten => s,n,Playback(is-set-to)
exten => s,n,SayDigits(${toext})
exten => s,n,Macro(hangupcall,)

[custom-cf-off]
exten => s,1,Answer
exten => s,n,Wait(1)
exten => s,n,Playback(call-fwd-unconditional)
exten => s,n,Playback(please-enter-your&extension)
exten => s,n,Read(fromext,then-press-pound,,,,)
exten => s,n,Wait(1)
exten => s,n,VMAuthenticate(${fromext})
exten => s,n,dbDel(CF/${fromext})
exten => s,n,Playback(call-fwd-unconditional&de-activated&for&extension)
exten => s,n,SayDigits(${fromext})
exten => s,n,Macro(hangupcall,)

I post the solution myself:

modified the app/script to not prompt for "enter the extension". Of course this limits to usability to using the feature codes from the IP phone only. Modify the code to the following, save and reload asterisk:

[app-cf-on]
include => app-cf-on-custom
exten => *72,1,Answer
exten => *72,n,Wait(1)
exten => *72,n,Macro(user-callerid,)
exten => *72,n,Playback(call-fwd-unconditional)
;exten => *72,n,Playback(please-enter-your&extension)
;exten => *72,n,Read(fromext,then-press-pound,,,,)
;exten => *72,n,Set(fromext=${IF($["foo${fromext}"="foo"]?${AMPUSER}:${fromext})})
exten => *72,n,Set(fromext=${AMPUSER})
exten => *72,n,Wait(1)
exten => *72,n(startread),Playback(ent-target-attendant)
exten => *72,n,Read(toext,then-press-pound,,,,)
exten => *72,n,GotoIf($["foo${toext}"="foo"]?startread)
exten => *72,n,Wait(1)
exten => *72,n,Set(DB(CF/${fromext})=${toext})
exten => *72,n,Playback(call-fwd-unconditional&for&extension)
exten => *72,n,SayDigits(${fromext})
exten => *72,n,Playback(is-set-to)
exten => *72,n,SayDigits(${toext})
exten => *72,n,Macro(hangupcall,)
exten => _*72.,1,Answer
exten => _*72.,n,Wait(1)
exten => _*72.,n,Macro(user-callerid,)
exten => _*72.,n,Set(DB(CF/${AMPUSER})=${EXTEN:3})
exten => _*72.,n,Playback(call-fwd-unconditional&for&extension)
exten => _*72.,n,SayDigits(${AMPUSER})
exten => _*72.,n,Playback(is-set-to)
exten => _*72.,n,SayDigits(${EXTEN:3})
exten => _*72.,n,Macro(hangupcall,)
; end of [app-cf-on]

--
Umer WaQar
TELEPACKETS INC.