Siri not working on ios 9.2 iphone 5s

Hi everybody,

I am having some problems with Siri.

She works when I use my Apple headset.

She does not work when I use the phone alone, without the headset.

I tried a full reset, after which VoiceMail worked. I then enabled Siri, no chance.

I found quit a lot of hits about this, and I am absolutely sure she worked a few days ago.

Voice Mail works, as does Audio / Voice Recorder. WhatsApp works and can record

audio as well.

Even after a hard reset, no Siri, except via headset.

This makes me think that one of the microphones is dead, and Siri uses just this one.

Now, which one is it, and how can I check the microphones one by one ?

kind regards,

Carsten