I’ve used Rattlegram to do something similar. It allows SMS messages to be sent without a cell network. You can use another type of radio to send the messages via audio. We use with 2 meter ham radio. You could also use with FRS radios. Each user would have the app on the phone. You type a message and click send on the phone, the phone generates an audio signal which is sent through the radio (you hold the phone near the radio while holding down the PTT button during sending). On the receiving end, the phone app hears the audio signal come through the radio and it decodes it back into a text message. https://play.google.com/store/apps/details?id=com.aicodix.rattlegram&hl=en_US
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Thank you for your reply. I was looking for something that is not reliant on anything else. I found something very similar to what I’m after and you will see that in the above messages. It said on the link provided on the above message that the application was discontinued however it is still operating and I have downloaded it onto many phones and it works fine in my village of very very bad reception.
Regards
Ray
I was able to install and use the app successfully but not on new phones… It only works on older phones unfortunately…
I think maybe you’re thinking of “The Serval Mesh” by the developers at “Serval Project” which is/was headquartered at Flinders University in Adelaide, Australia.
I don’t think this is still being maintained/run by the original developers… however I did find a copy up on f-droid (link below).
https://f-droid.org/en/packages/org.servalproject/
old showcase video: https://www.youtube.com/watch?v=u30KA7fk3v0
hope this is what you’re looking for. let me know if it is 
edit: it could have also been “B.A.T.M.A.N.” which seems older and can be found here: https://www.open-mesh.org/projects/open-mesh/wiki
Hi JamieX,
I did try The Serval Mesh and it worked ok within a small area but only on old phones. What I am looking for did not use WiFi and had a range of a few hundred meters between phones. It sort of turned your phone into a tower.
MOVISTAR is this it
Among the Canary Islands, Movistar has the greatest network coverage in Tenerife. A 30-gigabyte (GB) data plan with a 28-day validity period is available at prepaid data sim card Tenerife for as little as €10. Even in the most out-of-the-way parts of Tenerife, you can count on dependable internet connectivity.
Thanks Melanie,
I was after something not needing a company or towers… Just phone to phone…
Ray