I saw a post in a group in FB yesterday which says she had her iphone screen replaced for 25chf camera side not the front another one  says she was charged 100 chf, both in apple store and someone had hers replaced in manor where she bought the phone and was charged 200chf. The ones who had it repaired in apple store had an appointment online.

And another tip from a poster:

insurance will pay you if you had that option..

You could always get it delivered to your work address, then there'd be no chance of it getting lost in the post!  

Another post in FB:

"dropped my 4S on a tiled floor, damaged the internal screen (display) but phone still worked. The PodSpital in Plainpalais fixed it for me (for CHF 140.- mind you) but it was cheaper at that point than getting a new phone. Good luck!"

Anyone know of a place to fix a cracked Iphone screen in the Cornavin area?

had mine fixed on the top floor of Manor. They do it on the spot, in less than 20 mn

But I'm sure you can have it fixed in all the small phone shops, like the one on rue Rousseau

I've always gone to a place near Cornavin called Classphone, I've fixed my phone screen there for 100 chf and took a lot of my friends there and the prices have always been less than 120 CHF. They fix the phone on the same day 

Rue de Berne 25, 1201 Genève