The data rate from a noisy channel or storage can be derived from Shannon-hartley theorem.
This is why the old analogue phones could only do 56k for example.
And somehow, on analogue circuit switch phone call mode, still sounded better with less artifacts than most mobile phone calls!
"Across the world, we make 13.5 billion phone calls every day, using mobile phones. The average person makes or receives around eight phone calls every day, meaning that the US deals with around 2.4 billion phone calls across the 300 million cell phone users" that's from 2023 source.
Here's a 2019 one about US:
On average, people make and receive a total of 178 calls per month Of those 178 total calls, 93 are calls received and 85 are calls made
Not just older people either:
"80% of Millennials and 84% of Gen Z-ers use their phones during 2020 for phone calls".
Leased point-to-point DS0 circuits could do a full 64KBps if the whole circuit was 8-bit clean.