I only use my smartphone (Samsung Galaxy Chat) as a "pocket computer" (with WiFi) and don't use it to make telephone calls (I use a dual-SIM "dumbphone" for this). All the time it shows a cellular network signal indicator and reports that it can make emergency calls. Can I switch it off to save battery?
Some years ago, when I had a Benefon Esc! GSM+GPS phone, I could independently turn its GSM and GPS modules on/off. I wonder if this is possible in modern day smartphones.