My iPhone 6 was having GPS issues after I reinstalled iOS, it was fine before that. We brought it into this store and had one of the guys at the Genius Bar take a look. He ran some diagnostics and said everything was fine but would I like a new phone. He didn't check any settings. Replacement phones are $299 and I'd have to turn in my current phone. Long story short he didn't help, and kept pushing a replacement phone which we said we weren't ready to do. Later online I found out you just turn off "setting time zone". Problem solved.