Ye might find this useful, I've practiced it enough this week. I call it the minimal interaction of DSO pain method.
Them: "I got a letter though the door, about digital TV. I'm dumb and read the daily mail. Do I need to go digital?"
Me: "Do you have more than 5 channels on your TV?"
Them: "Why, yes."
Me: "OK, you've got digital."
And that's it. Some people don't understand the word analogue, never mind about digital.
I've just heard of someone who has paid for a £40 visit for 'the change' despite her daughter having previously attended to this some time ago. I'm sure the visiting engineers are regulary coming across this, and have to make up some switchover malary to get paid for the visit. In this case she got a new unnecessarily supplied freeview set top box :-(