Some people just won't let go.
There are tons of reasons not to upgrade your phone. Although, I almost take issue with the word "phone." Sure, that's part of what it does, but for most folks, that thing in your pocket is so much more than that. But that's not the point... Some folks just won't give up the one they've carried forever.
Maybe because it's paid for, or because they're afraid to upgrade and get lost in technology. My sister-in-law had an iPhone 5 til about a year and a half ago, until Apple basically just stopped offering new software updates, and it died a slow painful death. That's about to happen to a lot of those holdout folks. 3G is going away forever.
What's the big deal if 3G goes away?
Well, basically your phone won't work. Like, at all. You won't be able to make or get any calls at all. In fact, you won't even be able to call 911 with it. Its data stuff won't work either. You're basically going to have an old Nokia paperweight. But the "good" news is that you're at least getting this warning?
Technically, it all stops January 1st, but the providers are taking a more measured approach to total shutdown. AT&T customers can expect the final death bell in February of 2022, and T-Mobile's 3G service will be gone around June/July. Sprint is even shutting down part of its 4G service by July. Verizon is giving the longest lead time, ending 3G fully by December 31st of 2022, according to WMTW.
For real.... It's time to step into 2010, let alone 2021.
The only thing you can do is upgrade your phone. That's it. You'll need to. There's no more "sticking it to the man" by keeping that dino-phone. Carriers will likely offer deals on upgrades to new phones for the 3G devices. And talk to your provider. There's the slimmest possibility your device won't be affected, but I doubt it.
Good luck entering the new age, friends. It's going to be a very digital ride from here on out. By the way.... you can download a new version of Snake at the app store, if that's what's keeping you connected, haha.