I’ve just set up some old phones between my daughter and her school friends. I also looked at tincan but it’s quite expensive for each device + high monthly cost.

Using voipfone I have them all on a separate network with 3 digit phone numbers for £2 a month each and all connected with a grandstream voip controller + an old landline phone that I got on eBay / donated from neighbours.

It’s been so nice to see them all calling each other up and chatting. Retro tech is so good because it’s single purpose. No distractions.