For smartphones with high security, there are Cryptophone smartphones running Android and Windows Mobile 6.5. The ones running Windows Mobile 6.5 are like not 100% modern technology friendly that they should make the new Cryptophone device running Windows Phone with hardened security. But doing so may make things even worse. Firstly, the core of Windows 8 and 8.1 are already messed up with a bunch of backdoors used for the cyber-spying purposes so security-wise, you may as well avoid them and stick to Windows 7 and below or use other OSes instead if you feel kind of betrayed by Windows 8 and 8.1. In fact, don't even use the Embedded or Server variant either for the sake of security but then, they also contain some new technologies that you may want to look for their alternatives.
The concern coming from Cryptophone is that dozens of fake cell phone towers are discovered throughout US eavesdropping on Android devices. How technically messed up the nation is? Well, it's pretty much way too high and too far but the protection of privacy is just at the beginning with various browser extensions as well as the services with high security that will make eavesdropping and cyber-spying even harder.
The first problem is that the phones are being forced to switch from 4G to 2G mode while technically lying to you that they are still in 4G mode. It's awfully slow and you're better off without Mobile Data thingy on unless you use a god-damn secure phone like the Cryptophone or Blackphone. You can try Cyangenmod on your existing Android device but I don't know if that will help prevent this eavesdropping from happening.
