I switched to Verizon many years ago because it was the only company that gave me signal strength where I needed it. I raved about how great the signal was, for years, until now. All of a sudden, my signal is very poor. I'm dropping calls all the time, and I can't keep an app running to save my life. Where I used to get 4 bars, I'm lucky to get 1. This started after the most recent update. What gives?