What do you mean when you say the phone blacks out? Do you mean the screen goes black? This is what is suppose to happen. When you place the phone up to your ear the screen will turn off so you aren’t hitting button on the screen. If you are using the phone in speaker phone mode this could be part of the reason people are having a head time hearing you. The microphone one the likely isn’t that great so you would need to be fairly close to it. The only other think I can think of that would cause poor reception is if you are not getting a good signal to your cellular provider. Since it is a recent purchase, it could also be a defective unit.