Protips:1. Pay greenbacks for your phone.2. Use prepaid credit.3. Take out the battery before and after making a call.4. Throw it away after a couple of uses, ideally take it apart and drop into a water filled sink or river/sea etc5. Repeat 1 - 4, but not at the same shop.This is literally the only way to ensure anonymity on phones. The FBI can and do track suspect phones, even when they are supposedly turned off. Your phone can also be used as the equivalent of a long distance microphone by the FBI. This is not some conspiracy theory, take this advice seriously. There are so many caveats to using phones that you are forced to go to this level if you want anonymity.Fortunately, you can get all of the above for about $10-20 a pop if you look around. So, disposables are the future.