Yeah phone working, sit by it, and realise when checking the phone, for reasons unknown there's a recent missed call - that is the worst, especially if it's important and you've been waiting on a reply for a few days for them to have the time to call back. Often I wonder if the person only rang for a second or less, not long enough for the network to ring the phone but at times I get a voice mail ... so maybe not.

BTW, I don't so much mean a spotty network, just spotty voice calls over the network, where it seems there's not enough signal to carry the voice - apparently - but yet still capable for data over a hotspot delivering 100 to 300 kB/s minimum depending on factors like weather or time of day. From what I understand voice data is compressed via voice specific codecs. Most don't use more than 64 kB/s. [1] [2] [3] I think the silent calls are intermittent and by the time I've realised it would be probably pointless to test, however much of the time I could not say if the phone's browser was loading slow or fast as I rarely use any of the phone's functions apart from calls, plain sms texts, occasion to rare use of browser with preloaded tabs and creating a hotspot.

Likewise though not quite the same, over the past years I've had networks where the phone might ring but it is not situated well enough for the signal to be able to carry out any sort of conversation - and yet via a hotspot, downloading near to 1 MB/s without skipping a beat.

I still get some automated phone systems that are apparently not happy with the amount of voice data they are receiving even though what I hear is quite clear, and at times, have from near same time and spot, just rung other people who have not reported any difficulties hearing me. I've eventually learned to just hang up once the menu system goes awry and try a few hours later.

[1] https://www.gl.com/voice-codecs.html (has the codecs with a breakdown below the table)

[2] https://mobilepacketcore.com/glossary/codecs-audio-and-video... (brief overview including media streams )

[3] https://phoneguides.org/voice-codecs/ (Iffy coded site, refused older firefox, janky with a fairly recent chrome based browser)