Your cell phone only communicates with the nearest cell phone tower, which is usually no more than 1km away; everything else happens via the Internet.
The frequency at which your cell phone communicates is about 2 gigahertz and the radiation emitted is roughly like light, except that light has a frequency in the petahertz range.
In order for your cell phone to emit and receive this radiation, it needs a receiver/transmitter, which are antennas with a length of about 1/4 lambda to 1/2 lambda.
All other technical details can be found in the documentation of the transmit/receive modules or chips installed in your mobile phone.
Communication via apps like Signal, Telegram or WhatsApp is simply packet-based communication over the respective network.
There is a ton of information about this on YouTube and other video hosts, which goes into great detail.
