Had same issue - person on other end could not hear at all over speakerphone. Disabled VoIP. Completely fixed it. S10+ 1TB Sprint. For me, it was under SETTINGS -> CONNECTIONS -> VOICE NETWORKS.
As a side note, not sure what people are complaining about in terms of sound otherwise. I have hearing problems, and this phone is among the loudest and clearest I have ever used. I cannot hear on most phones, especially older iPhones (I has a 4S and 6 plus which were notorious at the time for being among the worst in-call volume of any phone on the market, and the 6 plus was the absolute worst overall phone I have ever owned and caused me to leave apple in disgust for such a buggy half-baked piece of junk. The lost a class-action lawsuit for covering up known issues with it.). The S7 edge had excellent volume and clarity when HD voice kicked in, but it was limited in when it could be used based on what device was being used on the other end. If you are having volume issues on the s10, disable VoIP, disable WiFi calling, and test it over the regular cellular voice. The volume and clarity for me cannot be beat, and the only time I have issues is with specific people due to their poor phone service on the other end.
Thank you to those who posted the VoIP fix earlier in the thread. I was really upset about my purchase until that fix, as I use speakerphone constantly. I do hope they fix this issue, though, as VoIP was a huge deal to me for being able to use data while in a call, and it is absurd to have such a glaring bug in such a pricey flagship phone.
Yes I'm having issues too with call quality. Thought it was my carrier Sprint, but now believe it is the S10+ phone itself. When I use the speakerphone, other people say I sound muffled or very distant and they cant hear me. I am only 3 feet away of the phone. I have to basically hold the phone in my hand in front of me, and then they can hear me.
I've had the phone since the launch date. I'm taking it back to Sprint and have them give me a new phone. It also has issues where it cant connect to Data until I reboot the phone. It will have full bars strength, and still not get any signal.
S10+ User: I haven't experienced bad audio quality on a call but I have been experiencing weird audio issues. My device seems to limit the volume of the audio coming from my music apps, even though the volume limiter is switched off. For example: While listening to music through my headphones, with the volume at 100%. At first, everything seems fine but, let's say I start a game while listening. Once I start the game, the volume and clarity get a significant boost. If I back out of the game to the homescreen, however, the volume and clarity decrease. Is anyone else experiencing this?
There are multiple posts in this forum which point to turning off one or more of the following:
1) VoLTE calling - seems to be an option on locked phones
2) WiFI calling - by default, my unlocked phone was set to use WiFI calling - open up your phone app and go to the Keypad display --> open the menu (vertical ...) in the upper right --> select settings. Under Call settings, there should be an option to turn off Wi-Fi calling.
Hope that helps!