Help Caller black list bug

[Stonecold2438]

The issue I'm facing is that there is that I'm unable to delete this 'Unknown' contact from black list as shown in the screen shot below. I'll cut straight to the point what happened was that I received a call from someone and while my phone rang the caller showed up as 'Unknown' (most probably a private number) and I didn't bother to answer and let it be a missed call. Following the missed call, I went to settings > call > call rejection > black list and I saw this weird contact named 'Unknown' prematurely added to the list. I tried to remove it from the list but it wasn't an option. I then proceeded to add a contact who was already on my phone into the black list and removed it from the black list with ease like how it should work. However, the contact 'Unknown' was added to the black list automatically (I supposed the phone system added it when I received the call) and now I'm unable to remove it from the black list. Any idea how can i resolve this issue?

 

[Hawker]

It it there by design.
It is there so that you can reject any unknown numbers
I have never used this feature, but this can mean one of 2 things:

1. reject any numbers with no caller id
2. reject any numbers not in your contacts.

My gut feeling is it is for (1.)

 

[jeff mutton]

I have a weird variant, one of my friends (who has an iphone) can receive texts and call from me, but not reply to them. He gets a red flag and is unable to continue.
I have no black list except the 'unknown' you point out, which I haven't ticked, and any other barring/blocking settings are off. I have tried deleting and re-entering my friend's details (as has he) and actually black-listing then de-blacklisting. to no avail.
Any suggestions desperately accepted.