This is useful for users who have many numbers and transfer the incoming call to the same Extension or Groups. 


For example: The user has 2 numbers 6564286063 and 6564286064 and forwards the incoming call to the group of 3 extensions: 304, 305, 306. They want to know which number (6564286063 or 6564286064) was called to reach them.


In this case, we need to do 2 steps:


#1 Set up the callerID prefix for the number 6564286064 as 001, setup the callerID prefix for the number 6564286063 as 002 as below:




#2 Set up 2 Dial Plans as below, this step is to help the extensions to re-dial the caller from the list history call of them:


    Start with 00x and has length of 13 (SG number is 10 numbers + 00x) then remove 3 leading digits and prepend