Why can I no longer make or receive calls from my Nokia Lumia 800?

[Windows Central Question]

Can no longer make or recieve calls from my Nokia Lumia 800.

Screen goes black and phone stops responding. Help please.

 

[ShinraCorp]

Re: Can no longer make or recieve calls from my Nokia Lumia 800.

Ok when does it go black? When you restart your phone? At a random time?