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