Hi pap.... Too bad about the call fails, but have you gone to your network provider and talked with them? If you can duplicate the problem for them with your phone, they should have an answer for you. But before that, try a "hard reset" on the phone, and if that doesn't work, reset your network connection -- it's an option within your Settings page. And FYI, your problem is NOT a common one experienced by others. I have NEVER had a call failure on my iPhone, and I live in the rural areas with a relatively weak signal.