I know this is a phone support issue, but there are almost no users on this forum for my particular phone model and I have gotten no response to any question I post under my phone model, so it does no good to post over there. I am hoping maybe someone in this general forum might be able to help me. Besides, the problem here is not unique to my phone model. Many other people with different phone models have the same problem. I am with AT&T. For the last three years I have used an Sony Xperia V on the AT&T network without problems. I have gotten great signal strength anywhere I go with the Xperia V. The GPS antenna gave out on it and I went looking for a new Xperia. I landed on the Z3 and order the international model (D6603). I got it and got a new AT&T Nano sims for it down at my local AT&T store and the phone worked right away. I downloaded the AT&T APN settings and got the data to work. The Z3 works and can make calls, text and it gets data service (only H+ though). I absolutely love my new Xperia Z3 (functionality wise). The only problem is that I have almost no signal. Now, I know that there is good signal strength where I am at because I have used my Xperia V in this area for 3 years and I have always had full bars of signal in my area. My Z3 only gets 1 to 2 bars, and sometimes none. My wife has a Galaxy S4 (with AT&T) and gets full signal in out home. We were on the road yesterday and I was on the phone with my mother and the call dropped because of no signal. My phone had the little red X on the signal bar. I looked my wife's S4 phone to see if she had signal and she had full signal strength. For about 20 miles (in an area I know there is good signal) the Z3 could not pick up any signal at all, but my wife's S4 had full signal strength and was doing facebook the whole time. I have done many searches about this and have found many other people that have the same problem on many different models of unlocked phones when it comes to at&t. I am just wondering if anyone has found a fix?