As someone who’s spent a lot of time working in the world of telco, it’s depressing how inherently unsecure the networks are in their design – Some networks attempt to improve on this which is good, however I simply wouldn’t call them secure.

My suggestion to anyone seriously worried about security – Consider the Internet access on your device no more secure than open WiFi at a coffee shop, and assume Calls/SMS are no more secure than a public conversation.

In short, use data/internet based over the top applications with encryption that you trust, obviously also trusting your endpoint/device too.

However remember that even that does nothing if your worried of location/device tracking.