There seems to be an extra transceiver built in in these Apple phones to contact satellites like INMARSAT and/or others. So no chance if the hardware isn’t equipped with this transceiver. Service is generally worldwide, but availability in countries is ‘only’ a legal issue.
Should be feasible by connecting a satellite modem via Bluetooth. There are messaging devices available for Globalstar (spot messenger) and Iridium (Garmin InReach). Thuraya even offers a bluetooth device offering satellite calls. Only someone has to program the software and I don’t know if the APIs of these devices are open/documented.
Tarrifs start from 15€ per month. It’s the same network and service which apple uses in their devices and continental coverage is worldwide, excluding oceans and polar regions.