The current configuration of the near field sensor ( @Chris_R, maybe you could change the topic to be more clearly that this is about, so others who have no idea what that sensor is are able to find it?) is a problem for me as well.
I often find myself in Time Zone settings or Calendar when finishing calls and i very often hang up by accident.
Interestingly, I had the same problem with other phones like the Nokia N8 or a cheaper Acer Android Smartphone (which is powered by an chipset of the same manufacturer as the Fairphone).
So tuning the Fairphone FP1 sensors would be great. A better sensor is on of the top priorities of my personal FP2 wishlist.