Lumia 800 - can't use headphones

Hello here,
My name is Adel and I would like to get some support for my Nokia Lumia 800.
Basically the problem is that headphones don't work with it, the phone doesn't recognize them.
I checked for dust, nothing.
I resetted it, nothing.
Tried to get to an earlier version of windows phone? Nothing.
Tried to change headphones, nothing.
Sent it to Nokia local store, after two weeks, i got back my phone with headphones finally recognized by the phone, but it was a short glory, one day later, the same problem is back. No headphones can be connected to the phone. And, I used the headphones that were given in the box when i bought the phone.
I really have troubles finding a similar solution over the net, feels like I am the only one in the world experiencing this issue
So guys, I would really appreciate if you could help me fix it please. 
Thanks and regards,
Adel Blackburn.

Let me also add that when the headphones are plugged in, the sound comes out from loudspeaker.
Just making sure. thanks