[Re-Titled by Host]
Using my iP7 with iOS 11.0.3, the volume during phone calls is working fine, so I can't say that your issue is software related.
Ringer volume: adjust it when you are in lock screen. Earpiece volume: adjust it while in a phone call.
If nothing changes, I would suggest that you try some other steps (and test after each attempts):
Force restart your device (since I don't know your iPhone model, please chose among the 3 methods in 1st paragraph of the following user support guide):
If your iPhone, iPad, or iPod touch won't turn on or is frozen - Apple Support
If nothing helps, take a look at this article:
If volume doesn't change, I'd try to install a fresh copy of iOS on your device. Make a full backup of your iPhone content, and then restore it to factory settings, and set it up as new (testing it before restoring from previous backup):
Restore your iPhone, iPad, or iPod to factory settings - Apple Support
In the issue still persists, contact your nearest Apple Store or AASP and have your device inspected.
Regards
Giulio
I do have the same problem, it's so annoying , I had to use the loud speaker in busy places to hear the caller.
My phone volume during calls is very low after the upgrade. I have to use the speaker. I have an iPhone 6 +
please help
I have the same problem.
when I'm in a crowded place, call volume on ear is very low but speaker/bluetooth/headset are all good.
iOS 12.1.4 (latest)
Iphone 6
same as mine!.. i spent 3 hours with tech support, and apple support. Ended up doing a comple wipe of my phone, and still no volume . Was told to go get a new phone
iPhone call volume low
