[from_iax]
exten => _804XXXX,1,NoOp(Incoming call to ${EXTEN})
exten => _804XXXX,n,NoOp(Extension is now ${EXTEN:3})
exten => _804XXXX,n,Goto(sip_phones,${EXTEN:3},1)      ; Strip the first three digits, and then go there.

[sip_phones]
exten => _2XXX,1,Macro(sip-vm,${EXTEN},0)


------------------------------------------------------------

    -- Executing [8042000@from_iax:1] NoOp("IAX2/10..7-2", "Incoming call to 8042000") in new stack
    -- Executing [8042000@from_iax:2] NoOp("IAX2/10..7-2", "Extension is now 2000") in new stack
    -- Executing [8042000@from_iax:3] Goto("IAX2/10..7-2", "2000") in new stack
    -- Goto (from_iax,8042000,2000)
  == Auto fallthrough, channel 'IAX2/10..7-2' status is 'UNKNOWN'