iphone - I can't hear anyone talking at all when I make a call unless I put...

[HayzaBabiie]

...it on speaker? Whenever I make or receive calls I cannot hear anything on the other end unless I put it on speaker and it's very annoying. How can I fix this? Please only answer if you truly know about this stuff, thank you

 

[Adrian]

Turn up the volume before and during a call is made