Is there such a thing? Given it's radio waves in regulated radio spectrum, I'm not sure such a device would even be allowed to operate without a license. This said, there are 3G Nokia dumbphones (e.g. C2-01). I just had to stop using one because my operator tore down the 3G network here, like in most of Europe. (2G was already down since some time).

Edit: there are even 4G-VoLTE dumbphones by the way.