Well, if you want as basic as possible, you'd probably just buy an old 2G, non-smart phone off eBay. Although these might be too small for texting? My only phone is an old 2G "candybar" phone, a TracFone LG100C (Verizon). But I only use it for voice calls, and rarely at that.
As for Android phones, I see some people saying that the old Samsung Galaxy II and III are tolerable, although I've tried the II, and stuck with my candybar phone. I'm sure there are several models of other phones out there that are more tolerable than average, but you need to look hard to find them. We have someone on the Facebook group who has tried over 50 phones!
I also have an Android phone (Samsung S7). What I do is keep my phone inside this faraday bag until I really need to make a call or send a text (not very often anymore). I tell everyone I know to email me when I'm at work instead of texting me. I also use the speaker function for the very few phone calls I make. Then I quickly put it back in the bag.