callerid - Sony Xperia Z won't name contacts on incoming calls

Whenever on of my contacts ring my phone, it does not display the caller ID and simply marks them as "Unknown".

I don't mean saying the contacts name out loud either- I just mean the caller ID isn't displayed on the screen for incoming calls. Even when the contacts are saved into my phone.

Please help! It's driving me mad and leading me to avoid all phone calls at the moment.