I got an unlocked iPhone 5s and put in my contract SIM. After my carrier eventually activated it I found the phone dropped signal to 'no service' constantly. I sent off for another 5s (unlocked and refurbished as well) and this one has similar issues albeit not as bad. I've worked out that I can stabilise the signal by turning off location services, so the problem must be related to apps that use location causing the signal loss. Has anyone heard of this problem before? I need a phone pretty urgently so i don't want to send another one back. Also I thought it might be the SIM itself (and therefore a network issue) but the fact that turning off location services seems to help goes against this.