Screen freezes when i try and select any contacts!!

I select contacts, press a name ie Adam Smith; the phone brings the name up with no contact details, then freezes and the phone goes dark. To clear you have to switch off and on again, then clear. So, basically i have no contact numbers or other details? I have done a hard reset and a factory reset; i have run malware bytes and AVG etc and nothing is found. My wife has the same phone and hers had started with the same problem. We are on sim only contracts with Vodafone? Thanks, Martin