Cell phones are inherently insecure

[Technician]

As a device that uses the public airwaves, cellphone signals can be picked up and recorded by anyone with hardware that allows it, and the hardware can be made at home with common components. Law enforcement has been using Stingray devices to intercept and listen to and record conversations for several years now and can do so without a warrant because the phones use public airwaves that by law are open for anyone to use.
What is less publicized is that the phones firmware can be flashed making the phone a listening device that can be used even when the phone is not in use. A virtual wire that can be placed on any suspect that uses a cell phone.
Now with a little bit of ingenuity anyone with knowledge of how a cell tower operates can make one of the devices themselves at home with parts that are readily available online or at a local electronics shop.
The new motto for cell phones is: never leave home with it.
And you were worried about Microsoft collecting data about how you use their products?

 

[DelJo63]

Very good. The issue not addressed is Frequency Switching (changing the Fq multiple times per second). This is a major component to private radio communications:

(wiki) At the beginning of World War II, Lamarr and composer George Antheil developed a radio guidance system for Allied torpedoes, which used spread spectrum and frequency hopping technology to defeat the threat of jamming by the Axis powers.[7] Though the US Navy did not adopt the technology until the 1960s, the principles of their work are now incorporated into modern Wi-Fi, CDMA and Bluetooth technology,[8][9][10] and this work led to their being inducted into the National Inventors Hall of Fame in 2014.[7][11]​

Many know that WiFi has channels, and as an analogy, the above is like using all 11 randomly for 1/10 sec each. However, it is not the same as scrambling (much more like encrypting).

Used today in all military radio.