I like this techie YouTuber Hugh Jeffreys, who makes interesting videos about mobile devices focusing on repairability and sustainability. This recent video was particularly fascinating, discussing the impending shutdown of both 2G and 3G in Australia, and the implications for calling. The main issue is that with both 2G and 3G gone, phones will have to rely on VoLTE to make calls -- but VoLTE actually isn't a universal standard, so it's not a simple matter of "does my phone have VoLTE?" It may depend on the specific implementation of VoLTE that a carrier uses (some of them are proprietary), so a given phone might work on one carrier's VoLTE, but not another. Since most countries are also planning on sunsetting these older networks, it may be a preview of issues everyone will have to face at some point.