I think Lenore Skenazy [0] is forming a national group dedicated to facilitating unsupervised play for children, which if you want your kids to not have phones would certainly help them. I've heard anecdotally that one of the reasons phones are appealing is it's a way to break free of being constantly monitored by modern day helicopter parents.

Another program I've heard of but don't know much about is wait until 8th [1], which is people promising to not give their children a smartphone until at the earliest 8th grade.

[0] http://www.freerangekids.com/

[1] https://www.waituntil8th.org/