What's the story behind the black screen? Has the phone suffered any kind of damage lately, like being dropped, exposed to liquids, etc.? Any recent software updates happened? Does the phone seem to be working normally except that you can't see anything on the screen?
The more you can tell us about it, the better we'll be able to help you figure out what's wrong with it.
1 
Hi Melanie,
What's the story behind the black screen? Has the phone suffered any kind of damage lately, like being dropped, exposed to liquids, etc.? Any recent software updates happened? Does the phone seem to be working normally except that you can't see anything on the screen?
The more you can tell us about it, the better we'll be able to help you figure out what's wrong with it.
Jerry Wheeler さんによる