If they are in your spam folder that is where they have been sent by the BT spam filters so the filters are obviously doing their job.
If they are in your Inbox mark them as spam and as stated, you are wasting your time trying to block them. The block feature really only works on genuine email addresses that you do not want to receive.
If the spam messages in your Inbox are always the same you could try setting up a "Rule" covering unique items about the emails in the Rule to move the spam to the spam folder.
