Hi mamoun,
We know the importance of having signal everywhere you are. When it comes to signal indoors we are not able to guarantee coverage due to non T-Mobile factors that can block signal(ex. internal equipment, satellites, components of the building's structure). If there is not signal when moving several yards or blocks away from the building, we need to file a service request. You can do so by contacting us, or chatting with us here http://support.t-mobile.com/welcome. Click "Live Chat" on the right and we can get you taken care of.