NSA has been collecting all electronic emissions worldwide since the 50s, including landline phone calls. Collection is one thing, finding a particular call is another, a huge task.
Every conversation passes through a Digital Signal Processor, which detects "key words in context". Anything interesting is tagged and recorded.
With current-day processors it is a fairly simple task.
Even with billions of call records logged per day, it does not take very long to find all of your calls. And "burner" phones have flagged ID codes which make them easy to single out for special attention.
Automated phone tree search will catch all of your friends too. There are user-friendly applications specifically designed to rummage through phone logs for persons of interest. All they need is data sources, and a starting point.
Phones are government-approved tracking and surveillance devices.
I have often wondered that...and lately figured the “government” was growing so that there would be a minder for every citizen.