The movie Greenland depicts cell phone communication working very poorly or not at all, as the world is facing extinction. Then at the end of the movie we hear from the survivors in the bunkers calling  “CQ CQ CQ This is Greenland Station is anyone receiving” several times,  then a response “Greenland Station this is Helsinki .. the signal is weak but we reach you.. We copy…” then “This is Sidney station..” Five over nine, this is Moscow station….”  

This is clearly represented as some type of radio communication. I believe it is most likely analog HF communication. This is very familiar to most Ham Radio (Amateur Radio) operators as a way to call out to see if anyone is there, then Identify ourselves by giving our registered call sign like “CQ, CQ, CQ, this is KI4CFS: Kilo, India, Four, Charlie, Foxtrot, Sierra. CQ, CQ, CQ” Then wait to see if someone responds. 

You can here it here in this Youtube clip: Greenland End of the World Scene II Ending Scene II 4K & 1080p II Greenland 2020 II

CQ – Calling Any Station (Morse Code abbreviation) is generally used in Amateur Radio (Ham Radio) “HF” bands using many modes. From Wikipedia: “CQ is a code used by wireless operators, particularly those communicating in Morse code, (— · — ·  — — · —), but also by voice operators, to make a general call (called a CQ call). Transmitting the letters CQ on a particular radio frequency is an invitation for any operator listening on that frequency to respond. It is still widely used in amateur radio. More on the history of CQ can be found here: https://en.wikipedia.org/wiki/CQ_(call) . “ 

5 over 9 (59) means that the signal was clearly heard and was strong. 5 means “Perfectly readable” and 9 means “Extremely strong signal”.  http://www.acsu.buffalo.edu/~maxwell/RSTInfo.html#:~:text=For%20example%2C%20a%20signal%20of,readable%20and%20extremely%20strong%20signal.   Five over nine is a “Signal strength and readability report” on how a message was received  

https:/s/en.wikipedia.org/wiki/Signal_strength_and_readability_report 

Ham Radio and Morse Code offer a simple but highly robust method of communication that can work with a backup battery or solar panel and rechargeable battery and does not need the internet or real fancy cell phone towers for basic analog communication. You never know when you need it! If you are not part of the Ham Radio community, maybe it is time you look into getting your basic Ham Radio License and radio, just in case or just for fun. 
Learn more about Ham Radio here http://ki4cfs.com/what-does-it-take-to-become-a-ham-radio-or-amateur-radio-operator/  or follow my Ham Radio Youtube channel. https://www.youtube.com/c/KI4CFSHamRadioMartinBrossman

– Martin Brossman – KI4CFS