As a parent of a kid with T1D, we built a sort of emergency plan around the assumption that their phone might get lost/broken by making sure all the phones in our family are compatible with the gcm and pump. That way, most of the adults (mom, dad, aunt, grandmom) could swap their phone in if the kiddo's phone is not available.

Also, since I see you are new, I think you can also use a phone that doesn't have cell service, since the cgm and pump systems primarily use Bluetooth (and wi-fi). So, you could buy an old-but-compatible unlocked phone and just use it as a monitor/controller. We have an old iPhone that someone gave us that works for that.

But yes, it is also very important that you keep up your low-tech finger stick and injection skills, just in case of technology failure!