Key point here being, if you try to do your own research and get a model that should work with your cell provider, there's no guarantees; they often have weird aspects of vendor or implementation lock built in.
(I'm in the EU, and I haven't seen a phone sold here (in a shop) that wasn't compatible with all available providers - to be honest, this problem has never crossed my mind when I bought a phone.)
2G is being shutdown too (IIRC, I had a 2G pay-as-you-go phone that stopped working years ago), and it would be surprising to me that a carrier would shutdown 3G before 2G.
Also, updates to SMS implementations eventually broke SMS on the good network.