24/7 support is pretty important to some. This should count as a significant detrimental change to their contract and thus mean people can leave/transfer without penalty.
It's certainly a detrimental change in my view, working 00:00 to 08:00 as I generally do, and have usually found short/no queues when I have rung in the past at some hour in my 'day' (like 03:00)
I guess that the hours they suggest fit in with more regular users, and is understandable, but there are significant downsides for customers who still find there to be queues in the new hours, and I'm also guessing that if this means that some "antisocial hours" allowance has been scrapped, it may also mean many staff will be losing money.
Added to which, there may be instances, since so much of the PN engineering work is overnight, that a customer wants to phone with a problem, but then finds they are ringing outside the new hours (I would not have known if I had not seen this on TB this morning), and such customers may quickly become ex-customers, or at the very least, negative towards PN and steer business away (and then leave when their contract expires).
With the price hike coming fairly soon, as well, it looks to me as if PN will be happy to see their customer numbers drop - just might be a gamble if the numbers drop too much!