Maybe it's a regional thing. I'm German and things are often shittier versions here than anywhere else. I haven't had a phone conversation that felt like a latency under .5 seconds in 5+ years.
I'm asking, because whenever I hear people complain about phone software that just breaks, it's almost always Android, and with good reason: They have to support a lot more phones than iOS, and Android is a lot more open.
So I just wanted to air the idea that you could try with an iPhone. iOS may lack some of the feature Android users are used to, but in my experience, it's just more stable, and I don't at all share the sentiment that "phones are unusable" or that the audio quality is bad or anything of the kind. If there's one device I can always count on working, it's my phone.
Recently I noticed that in specific location 3G UMTS call quality is much worse than 2G GSM...
(and there is that weird VoLTE, but it apparently requires specifically supported phone by operator with branded firmware..why!?)
Unfortunately it does not help you if you want to use the regular dialer to access the telco voice networks and/or nobody you know has the app.