So I called my cell phone company and told them I was concerned about my privacy, etc. They connected me with someone in the know. Basically he said that if I make a call, the cell tower it hit is logged. Voice mails and missed calls are not. If I answer my cell, it's also logged, and that information is not available to any LEA without a warrant.
He could have been talking out of his behind though, and I might have missed what he was trying to say, because he sounded busy and was talking fast.
Also, I'm in Switzerland, so it may be different in the USA.