If you had a Stick in this situation, you’d be Stuck, but as it’s a box and not a Stick, it has an Ethernet port, so you can wire it to your router that way, regain control of it with the mobile app, and set up the WiFi.
This does mean that you need to position the box within reach of a mains socket for power, and with an HDMI cable to a TV so you can see what’s going on, and an Ethernet cable to the router to make the temporary connection so you can set it up, and this may be easy or hard depending on how your kit is physically arranged; but it should be doable.
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.
