First they tell me you can't have Smart Divert on a residential line, so I go through all the hassle of converting a line from a residential to a business line.
Then I discover that you can (what you can't have is some package we don't want bundling some other service we don't want with Smart Divert).
Then I get them to convert the line back - this breaks the direct debit I've set up, apparently - as this saves us about £40 per quarter.
But it worked in the end.
At least it worked on Saturday and now it don't work no more. I think they've either taken Smart Divert off the line or changed the pin code (despite being asked not to).