You might want to consider if anyone else could have had access to your account, or a live NowTV device or app of yours, and bought something. Which, without a Payment PIN in place, is something even a small child could do.
So, go to My Account/Bills & payments. This should show you what the payments are for.
If you then still disagree with them, or if there is a discrepancy between what you have been charged and what you see there, proceed as @gavs82008 suggests.
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