iPhone 5c Time and Date won't stay correct iOS 8.3
I have a blue iPhone 5c running iOS 8.3
The time and date will randomly change, the time could could go anyway from 20 minutes off to over 20 hours off, the date usually changes back to the previous day. It has gotten to the point where at least 8 times a day I have to fix the time. Usually it resets when I lock the phone or if the phone isn't connected to wifi. I've brought it to apple and they didn't fix it. What else can I do at this point.
iPhone 5c, iOS 8.3