Hi Bud, sorry no they do not. Here in PNG you have to purchase a new sim card. The boys we employ from Kokoda come in and purchase a mobile phone but when they go home they leave them here in Port Moresby for when they return as they are of no use back home.
Some mobile phones you can change the sim card on but some brands you cannot.
It is now 2019 and Mobile phone coverage on the track is still limited. On track there are only 2-3 locations where mobiles will work whilst trekking. These locations are typically close to Owers Cnr and or Kokoda side of the track.
All trek’s that we run have Satellite phone coverage so that we are able to communicate effectively with a trek that is in progress.
We also have Satellite tracking which we use to monitor a trek in progress and for friends and family back home to know where the trek is in real time.