I have had this issue intermittantly on my iphone 5c. And now I cannot get it to unfreeze for about 2 weeks. This occurs while using wifi and cellular. The ios is current and I have available storage. Email is at 30%. What else do you need to know in order to analyze and fix. I had submitted a problem report and because it started to work again for about a week, I closed it. I have deleted the app and reinstalled.