@Anonymous User
No, it’s feeling its way towards the highest speed it can support for you, and this can take up to ten days.
But if the violent fluctuations are still there after 24 hours, rather than just little ripples now and then, get back in touch with the broadband people, and get them to recheck the line.
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.
