iPhone Speaker Microphone not working.

Hi,

Microphone works fine when:

-Talking on the phone (no speaker)

-FaceTime audio and video

-Voice memos

-Skype (camera off)

Microphone doesn't detect anything when:

-Turning the speaker on in a phone call

-Siri

-Skype with video on or speaker

When inserting headphones, everything works perfectly.

So why the phone stopped working well?

iPhone 5S iOS 8.4.1