How to block all incoming calls (and messages) that are not from the contacts in my contact list? Basically I just want to white list my contacts (and black list some of them). I couldn't find such functionality in standard call filter application or Truecaller. Is it possible to do so on Windows 10 mobile?
As a workaround, you could use 'Quiet Hours' feature and filter the ones which you want to receive calls/messages from. since it is not possible to block all incoming calls.
No, it is currently not possible to block all unknown numbers. For now you'll have to manually block each call you want to ignore.