iPhone went blank

Try a forced restart of your device, following the steps provided in the first chapter of this guide:

If your iPhone, iPad, or iPod touch won't turn on or is frozen - Apple Support

If nothing changes, have that device inspected at your most convenient Apple Store or Authorized Service Provider: Apple - Find Locations - Location Selector

Regards

Giulio

Sorry about that.

At this point, as already suggested in my previous reply, make an appointment at an Apple Store. They will check your device and give you all the available options.

Regards

Giulio