Before arranging for a repair or visit to a genius bar, first try a Forced restart
Click here > Force restart iPhone – Apple Support (UK)
If no better you should probably arrange a repair
Click here > iPhone Repair & Service - Apple Support
Or
Click here > Contact - Official Apple Support
Anything other than Screen or Battery may be a replacement phone and the price is in the article under "Other damage"
See also: Get your iPhone, iPad, or iPod touch ready for service - Apple Support
There is no compensation for hardware that fails during an update outside of normal warranty period..