Or you could just buy a 20$ piece of shit pre paid flip phone without all the high tech shit, just a thought.
You are tracked without smartphone or GPS, all phones, operators, log the phone signal triangulation, depending on the area and density of phone company they have got you placed anyway, abeit not to the last foot like GPS does.
The NSA are very good at voice recognition and have been for a while, so burners are really only good if you use a voice scrambler that they haven't hacked, if such a thing exists. Looking at the form book, it is likely that a large percentage of the voice scramblers, as well as "anonymous" messaging apps etc.are all backdoored ,compromised and rooted to fuck by the spooks anyway.
Lucky that they are chasing terrorists not potheads eh...
If you want to do something that you don't want to have to explain to a Jury, understand the tech, just slip the phone into your wife's handbag for the time you want to go AWOL and let the spooks track "your" progress around her route of Hair salons, coffee mornings and Anne Summers parties .