Generally setting cptone PH should allow the supervisory disconnect to operate, but you may need to enable a custom class. In many countries the tones vary from region to region or even city to city.

Best thing to do is to get a wireshark trace of the end of a call when the PSTN side disconnects and the disconnect tones are played out from the exchange.

Save this packet capture file and attach it this thread, we can extract the audio and come up with a custom tone class for you to try. We only need around 10 seconds of the tones.