As to your question: It depends on which apps (or malware) is running in the phone. For instance, when I am in the Google app, it is constantly listening for me to say, "OK, Google" which then takes your utterances and sends the audio to the Google servers where it is decoded and the transcription is sent back to your phone. Whether doing a search or telling it to make a call, the mic is constantly listening and communicating to the mother ship.
For true Shabbat, I would recommend that you not turn on any electronic device nor do any human-centered work. Rituals like worrying about electrons takes your mind off G-d.
You may have heard about telephones designed to be used on Shabbat use a photocel/LED beam detector so when you press the buttons you are interrupting the flow rather than creating it. Those were the old hard-wired phones some years back. Of course, that would trigger the phone company to run relay switches to complete the calls.
They did the same with elevator buttons. But of course, on the elevators, in the end it would activate heavy-duty electric motors to move the car.
If you really want to celebrate Shabbat I would humbly suggest that you use that time to get into the scripture and keep your focus on G-d the entire day. He does not want us to practice certain rituals like avoiding electricity. Instead, He wants us to turn our minds to Him and spend time with Him. Prayer and study is the most pure of offerings.
If you have to ask "Is this a sin?" I suggest instead that you ask "Will this help me get to know Him better, and for Him to get to know me better?"
He wants you to know Him, and He reveals himself in the scrolls. In Genesis, it says that Adam walked with YHWH. I believe that is what the LORD desires from all of us.