I don't think the NSA gets it directly unless they installed an app on your device which if they're using Google and Apple to do that for them could be fairly hidden.

But a lot of the apps people have installed do listen when people don't expect it, for commercial purposes. That information is then available to the NSA or any other law enforcement around the world basically at will. But there are things you can do to prevent that. Like not installing untrustworthy apps and if you have to, disabling their access to the microphone, storage, etc., if you have a device that allows that level of control.

But there isn't a blanket, listen to everything and record it kind of thing going on or you'd be using a lot more bandwidth. Most devices aren't powerful enough to even do voice recognition beyond a few key words, but definitely not full realtime transcription, so the audio would have to be passed to a server.

The real issue for now is things like keyboard apps and messaging apps that send everything you type, or the multitude of apps that don't actually do user to user encryption, but decrypt in the middle so the data can be stored, combined, and compressed which makes it available to commercial interests and law enforcement.