Some aircraft (but by no means all) are no doubt equipped for mobile phone service, but as far as I am aware, a mobile phone, suitable to the area of operations is not yet a required item for flight crew.
Particularly on the Helsinki flight, they would have had to shuffle sim cards and service providers to call the number, and it is by no means certain that mobile phones are a reliable form of emergency communication.
Or have I been out of touch too long?