The NowTV app is available on other devices. Do you have a smart tv with apps, a games console, a tablet or smart phone? The smart phone option may not be the best viewing experience but at least you wont have wasted your pass.
I assume they would refund you if you have a box they have stopped suppporting assuming it is a NowTV box and not some other device.
Can I assume your talking about the Now TV white box for the device?
If so that device was decommissioned back in October.
Personally speaking your best option would be to go with an Amazon fire stick, much more reliable than the Now TV stick which is what you might get offered
What was the make and model of the Smart TV you bought?
Are you not able to "cast" from the NOW app on your mobile to your Smart TV? This way you could still in theory use NOW on your Smart TV without having to purchase another device.
@Anonymous User @gavs82008
You see why you should do a little bit of research before spending your money?
Anyway, as Gavs suggested, you could try casting to your TV or buy yourself an Amazon Fire Stick, which most users prefer for it's quality and performance.
Either way, you'll have to spend a little more money to get yourself back on track.