How come i call i can hear them but they can't hear me

[AC Question]

I try calling and I'm using headphone to talk I can hear them but they can't hear me unless I put them on speaker then they can hear me. How come? What do I do?

 

[anon(632115)]

Does the headphone have a microphone, too? If not, that's why you have this issue since plugging into the socket will disable the phone's mic