How can i record my greeting, something like this(eg. after 3 rings a message, then another 3 rings another message so on..) on ip phone 7940 or 7912.
You can in Unity. Set the subscriber in unity to specify what you want to do after the caller has left a message... hang up, system transfers, etc.
Caller rings your first number
Leaves a message, Unity lets you take the message, not take a message and supply a command to hang up, or pick a function. (callhandler, system transfer etc)
so in your scenario:
Caller rings your first number 3 times
Rolls to Unity
Unity plays message
Unity will not take a message but do a system transfer to another ext. "Please wait will I transfer your call"
Unity transfer to ext.
Phone rings 3 times
rolls to Unity