Here is a recording of Glenn Mulcaire using social engineering to reset the PINs to voice mailboxes to which he did not have authorised access. (At least, that's my understanding.)
He appears to say to the operator, "Do you want the DDNs on these, or - you should have them anyway, shouldn't you?" The operator replies, "I'll have that [information] here."
My question is: what are the DDNs to which Mulcaire is referring? I.e. which words does the initialism stand for, and what thing is referred to by the name composed of those words?
Here is a possibly related question.