If you have the NowTV app on your TV, then it will work with the TV remote, but not with a NowTV remote.
Or are you using a NowTV Stick with the TV, and trying to have the NowTV remote control the Samsung TV, which it can do (only) for On/Off and volume up/down?
If you can clarify what you are trying to do with what pieces of equipment, we can likely help further when we understand.
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.