Welcome to the forums stampmann.
I'm not aware of any £25 BT package.
BT residential landline rental payable by DD is £11/month (£10.75 if you opt for online only billing) and, adding their top package,
BT Together Option 3 at an additional £9.95/month, the total to only £20.70/month - so what are you paying £4.30 more for?
Anyway, sorry to have to bring you down from the euphoria of the marketing spiel but, in reality, you're not getting free calls - you're paying £14.25/month, in advance, for calls you might
or might not make. Indeed, you'll be paying that even when you're away on holiday and not using the phone at all!
It may not be too late to change your mind and, apart from using this excellent site as you obviously do, I'd recommend a few minutes reading
bbb_uk's suggestions for reducing your costs and/or
my own (they're very similar but mixing and matching to suit your own circumstances is best).