HTC One S :: Call Somebody Can Hear The 'dial Tone' Twice And Then It Just Stops?

I'm currently the owner of a HTC One S but it started to act weird since a couple of days ago. More specific, when I am trying to call somebody you can hear the 'dial tone' twice and then it just stops and goes back to the telephone/contacts screen. Furthermore, when I am receiving calls the phone rings one, two or three times and then it stops for one second. Then, it starts to ring again two or three times and it ends et cetera ,, then the phone says that I have got 2 or three missed calls from this particular person (I tested it with my friend's phone and I just called once (and let the phone ringing for a while). Also, if i managed to pick it up within the two rings the conversation only lasts for a few seconds and then the phone goes back to the home screen.

Does anyone faces similar problems and has a solution? It's driving me crazy!Signal issues? By the way, sending and receiving text messages does not seems to be a problem. Also, I did a reset to the original factory settings but the problem still exists. The phone also contained the last availble updates