Block withheld calls - Not working

[#1]

According to the online help:
Block withheld calls Dial * 2 2 7 #
When dialling *227#, I get a voice message saying that the service is not available...

[#2]

Hi - you need to add the anonymous call reject feature via the home phone control panel first

[#3]

That's via the Call Features tab at the cost of £4.00 pm