GPS Tracking, can my employer track my location

Hi all, I tried doing a google search but didn't really find anything that was helpful so I figured I'd try here, also tried looking for similar threads with not luck, so here goes: can my employer track my location using my iphone 3gs which is my personal cell phone? I never signed anything to my knowledge or downloaded any app connected to their company that would allow gps tracking, they do not pay for my phone or have any ties to my personal cell phone, or installed anything or nothing! I know for a fact that they give out cellphones to other field employees and that they can track their gps location either using their cell phones or gps in the company cars, but I'm a lowely receptionst and I was just curious bc I received a strange phone call from my boss's boss who I hardly ever speak to and that got me wondering.