Hearing volume is too low, unable to listen caller's voice in iphone 6. Every time I hv to put my phone in speaker to listen caller's voice. Pls suggest to fix it.

If you have a distorted Sound issue on your iPhone --> If you hear no sound or distorted sound from your iPhone, iPad

If you are not able to hear the other person, click this...>If you can't hear a person on a call or voicemail or if the sound isn't ...

If you only hear through speakerphone mode --> If your iPhone is stuck in headphone mode - Apple Support

If the other person is not able to listen to you then please click this--> If the microphones on your iPhone, iPad, and iPod touch aren't ...

If the above options do not mitigate the issues then Contact your carrier and then Contact Apple Support

How do I turn up the volume. I cannot hear on my iPhone without turning on the speaker