we have a centralised setup of ccm 4.2(3) and the ip phones are in different cities,we also have a trunk to USA also.i have blocked offnet to offnet calls for the external transfer to PSTN.But as the PSTN line is connected to the central site gateway router,people from other cities call to the central site ip phones and get transfered to the PSTN numbers,which must be prevented.please do suggest me what can be done to prevent this
There can be more than one way to do this. The simplest one I can think of is to have two lines on each of your phone. First line will be used for local outbound and inbound calling. Second will be an internal extension which can call all other internal extension but not to PSTN. These two lines will be in different partitions which cannot call each other.
The second lines of phones in different cities can call each other but not to the first line. So calls cannot be transferred to remote side PSTN.