An earlier post was referring to the buzzing effect, not necessarily the phone itself.
The buzzer is just an example. Remove the buzzer, and you're still left with all the tantalum resistors and capacitors, which still involve all the same problems, and which also exist in every other microelectronic device on the market. There is nothing unique about either buzzing or phones in this regard. It's just one particular example. And once you widen your focus beyond one particular use of one particular element, you see that these issues exist everywhere. Buy anything with palm oil in it? (Just about everything has palm oil in it these days...) Well, do you have any idea what happened to the people who used to live where the palm oil plantations now are? Most of them are dead, and the rest are practically enslaved.
Also, please note that (as I stated earlier) the vast majority of the rare earth elements used in these applications do not come from the Congo. Yes, there are lots of human rights issues surrounding resource extraction from the developing world, but (a) these issues are common to practically everything in our society, not just electronics, and (b) the vast majority of theses resources come from the developed world (Australia, Canada, etc) anyway. Food production is, in many ways, much worse - but that doesn't support some people's desires to locate all of the evils of the modern world in mobile phones.
Nevertheless, I'm still using a phone I bought second-hand many years ago, at least partly through concerns over these issues.