Wait, do I understand correctly that my phone is being abused as part of a global botnet for Apple? How do I disable my iPhone being using to relay data?
It's a stretch to say anonymized reporting of nearby lost devices is abuse and part of a botnet, but you can turn off the U1 chip in settings. Privacy > Location Services > System Services > Networking & Wireless
Apple then shares this data with the US federal government without the requirement for a warrant, whenever they ask via a FISA request. No probable cause of criminal activity is required: it can be used for pure fishing expeditions, or parallel construction.
I don't think it's reasonable that using the GPS functionality in my device also means the device manufacturer should perpetually receive a real-time log of everywhere my device goes that is then made available to federal investigators whenever they wish to see it.