Sound low on calls using iPhone

Same exact issue. I can hear the ringer fine & speaker phone works fine, but when I have the phone to my ear I can barely hear the person on the phone talking. It’s like they’re far away. I did double check that the volume is all the way up for that & it is. My issue started around the same time as your post earlier this month.

I have tried the trouble shoot they posted to your reply & it still doesn’t fix it.

If you hear no sound or distorted sound from your iPhone, iPad, or iPod touch speaker

https://support.apple.com/en-us/HT203794