How to block a number in Sony Xperia J I intend to block a number that is in my contact list. 
Unfortunately I can't find any option to block it. I was told that I should add it to some Reject list.

When I open the contact and press Menu, I see only 4 options:


Modify
Send contact
Delete contact
Set as default


Where should I add it to the reject list?
Shockingly, you can't block calls with Xperia phones.


  Unfortunately it's not possible to do this without installing any 3rd party software. I know that Truecaller has this function if you want to use a 3rd party app.


Source: official Sony forum

You need to download 3rd party softwares that are mentioned earlier:

TrueCaller

Calls Blacklist