Cell phone operators and internet service providers cooperate with national security agencies in almost all countries of the world. They can do so for any of their company’s customers. Government surveillance exists in some fashion in most countries worldwide.
In many countries, such as the U.S., security agencies first have to present a warrant to the cell phone operator. Only a court can issue this warrant so that law-abiding citizens have nothing to worry about.
However, if cell phone operators want to, they can provide government agencies data from any customer’s three-month usage. If a security agency has tapped your smartphone, you usually don’t know it until it’s too late.
Phone conversations are usually useless because they require too many resources to analyze. So agencies or hackers who want to listen in to your phone calls don’t have any incentive to do so.
It’s much more productive for them to set up special bug devices in a target’s home or place of business. You can use radio wave detectors to check if there are bugs present in your home or building.