In that case, IMSI catchers are the least of your concerns. A functional phone is tied to a carrier who can triangulate your position or at least get the closest tower to put you within a radius. A mobile phone is a snitch in your pocket. As others have said, the best defense is not to use one. You should ask yourself how often it is necessary to make or take calls when you're away from your house. Yes, it's convenient, but if you're honest about it, you could leave your phone at home 95% of the time you go out and get those calls when you come back. That would go a long way toward protecting your privacy. Also, use cash as much as possible. Your credit/debit card is another snitch in your pocket.