my iPhone 6 screen begins to jump around and shows digitisation freezes then becomes completely inop
my iPhone 6 screen begins to jump around and shows digitisation freezes then becomes completely inoperable
iPhone 6, iOS 12
It would not be economical to repair all the hardware issues on this obsolete phone
But if you do want to for sentimental reasons...
For service or repair:
https://support.apple.com/iphone/repair/service
Anything other than Screen or Battery may be a replacement phone and the price is in the article.
You can see additional service information within the following article:
Get your iPhone, iPad, or iPod touch ready for service - Apple Support