Methods and apparatus for determining whether a phone call is an inter-MTA
or an intra-MTA call. Call detail records are retrieved that describe the
call. An originating MTA is determined using the originating NPA/NXX,
while the terminating MTA is determined using the terminating NPA/NXX.
The determined originating MTA is compared with the determined
terminating MTA to determine whether the phone call is an inter-MTA or an
intra-MTA call.