@Anonymous User
Welcome to the forum. I think that's just the way the offer is set up using the same system as if you were paying for it but then you should see it discounted down to £0.00 before you place the order if it's the same system as they used last time.
However if you're not sure or it looks like they are trying to charge you pop onto live chat and check with them. You can get to live chat from the Contact Us page
https://help.nowtv.com/get-in-touch
(expand the Anything Else section at the bottom for options)
