Looking for Component Guidance to Build Phone

[CtrlAltNoot]

I'm wanting to build a featurephone (dumbphone) for a friend that fits into a custom 3D-printed shell. I want to use a non-touchscreen display (e-ink is okay) and a physical numpad. I would love some guidance on component choices to help point me in the right direction with schematics. I've made PCBs before, but I haven't worked with anything relating to cellular networks. Thanks!