@Ashley
I have no idea for Broadband, though I could answer for Memberships.
The people you need to get in touch with about this, Now Broadband, can be telephoned on 03300 412518, which NOW Broadband Members can call 8am–8pm, 7 days a week.
Give them a ring and see what they say.
And please let us know what they say, so we can better help the next person with this query.
Set a Payment PIN on your account so that no-one but you can buy memberships on it. Check your bank accounts monthly for any other unexpected payments to Now. That way you can at least nip them in the bud, while you and Now figure out whose fault they are.
If you take an offer that comes with a ‘free trial’ of Boost or another Membership, Cancel them straight away. You will still get the full duration of the trial, and if you decide you do want to continue with one or another of the trial products, just revisit the Cancel, and UnCancel it.
