Our trek groups carry a satellite phone and two (2) VHF radios for emergency communications. Our logistic base at Sogeri maintains a 24/7 watch.
You can use a mobile phone in Port Moresby, Sogeri and Kokoda. There are also a couple of places along the trail where it is possible to get a signal. The normal exorbitant global-roam prices apply in PNG however it is possible to get a local SIM card on arrival at Port Moresby airport which is a much more economical way to call home.