For those who have a "no data" plan - I found that was a problem for us with our occasional texts. We could not send/receive picture texts (MMS) or group texts.
OK for us, but if one of the kids texted some of us as a group, like to all meet at such and such place at a certain time, my wife would not get the text. If a text included a picture, she would not get it. It just won't work to tell people to not send picture texts or group texts, they won't remember.
There may be some plans that enable some limited data for MMS, but don't provide data for other connections, but I'm not aware of any.
I'm not sure why OP said they want to get rid of their smartphones, but they are still using smartphones (their existing iPhones)? I guess the key is they wanted to get rid of data charges, which is really separate from 'smartphone'.
What's been working for us is Ting (heard about it on this forum). We don't use much talk/text/data, but we want it when we want it. With Ting, the rates are pretty low for low usage, and I added my phone to the account for just $6/month (usage is combined). It's not a great deal if you use a lot of data, but for us it has been great. We are more likely to use data if go away for a w/e or something, though we can still stay on wi-fi a lot of the time. But the occasionally higher monthly bills for the data are fine, as our averages stay low.
Our typical bill is ~ $26 for 2 lines (
$13/line for people skimming the post) with occasional bills in the $35~$40 range when we are travelling (these numbers include the fees, which are added on to 'usage'). We just got to the point that we didn't want to go without data for the times that we really could benefit from it, and at these rates it just isn't painful at all.
https://ting.com/rates
-ERD50