Hi there as far as I no there isn't a fix for this and it's hardware issue.
If it's still in warrenty go and get a replacement.
You can check out information here [https://discussions.apple.com/thread/5372052?start=60&tstart=0]
There's plenty of cases to read about on here and some success story's on how to get around it involving puting phone in the freezer I'm not 1 for doing that but if phones out of warrenty and it's basically a brick then there's no harm in trying.
Hope u get it sorted