Do you have a good reason to believe authorities might be monitoring your phone specifically out of the hundreds of millions of people the could pick from?
they don't have to monitor any specific phone. that would be like, collecting the info but throwing away most of it. if they are doing something, they are monitoring at the provider level.
They don't have the capacity to monitor every single phone or conversation.
it does not take much processing power to search in SMS messages as they are sent. that's just very small plain text messages.
phone calls would be different, but unless it's volte, processing is easier than transmission, because of the very low bitrate.
If you just go about your life minding your business
"minding your business" means not protesting to leave a foreign country in peace. from a point of view, it's not our business.