If you have a phone with GPS or one that has "E911 capable" printed on the box then your phone is trackable. Supposedly the e911 is only supposed to be activated when you are making an emergency call, but there is nothing to keep the phone company from using it to know when you are down at your local pub, or getting a manicure at the salon. Many don't really mind, others feel this is an invasion of privacy. If you fit into the the latter group then you might want to stop cell phone tracking by getting a blocking device.
Get a cell phone jammer. There are a number of cell phone jamming devices that will work from an area of 10 meters to more than 200 meters. You can find them at Amazon.com or any spy gear store such as spyworld.com
Know what you are getting. Note that some block GSM and CDMA, which will disable phone calls from being made or received, but this may not keep the GPS function from working, which will allow you to be tracked. Make sure that you get a device that blocks GPS as well.
Switch it on. Depending on what type you get ,you will block signals from 10 to 200 meters. Obviously if this is just for your personal use, 10 meters is more than sufficient. They all come with a built-in rechargeable Li-ion battery, which usually lasts for two hours of signal jamming. And make sure to get a car power adapter.