Well, before the Internet, the police could get a warrant with just cause, and tap your phone. That would end up as a box of reel-to-reel tapes that someone would have to listen to and transcribe.

Now, in the electronic age, they could demand that the phone company keep records of every phone call made by every single customer of theirs, and have it uploaded to the NSA computers for real-time analysis using AI. Different scope entirely.