I'm not sure that this is a US airline recording, I'm actually not sure what this is. But when an amendment must be done to an air carrier's dispatch release (diversion, change of required fuel, alternate, altitude, aircraft, etc), there also must be a note on there of what dispatcher authorized the change (initials) and when the change was made official (time). Usually such conversation/transmission would be "Comair 321, I'll show LGA as your alternate now, same dispatcher, time 0042z." Same dispatcher, meaning the same dispatcher's name that is on the release who originally worked up the flight's paperwork.