As reported in Bad outgoing signal / call partners don't hear me or only interruptedly , I quite often had the issue that call partners would not hear me (or only interruptedly).
As I was reading about some network switching issues on some other unrelated Android article, I played around with the network options, and my (somewhat crude) fix has now been to limit the network capability of my phone to 2G most of the time - then those signal problems don’t seem to occur. Although I haven’t tested that thoroughly yet, I didn’t hear any reports about bad call quality from my call partners anymore. It’s not ideal - when I want better internet connection I have to go into the settings and switch; but typically when I’m using the internet more heavily, I have WiFi access anyway. I can’t really speculate about the reasons why it works better to only use 2G, but maybe it can help someone here with similar problems, or maybe someone else can shed a light on the reasons ;).