Can't update my iPhone 5 to IOS 8?

When i stream the update from my phone, it says it takes around 30 hours to update, then after around 2 hours it says the download has failed. When i hook it up to itunes on my computer it says it takes up to 100 hours to update, and the hours keep changing. I can't restore my phone because it requires to update. I've tried everything; turning my phone on and off, putting it in recovery mode, and even redownloading itunes. Please Help! My iphone 5 is currently running on IOS 7.1.2

Try calling apple. Or go to there website. I always call apple when I'm having trouble with one of there devices