Just to be clear... Norwegian lets you book and pay for an upgrade, without even entering payment details again?!?!?!

I suspect not, so basically you went through a series of steps, including adding payment details, for something you expected to be free?

Unfortunately this is a lesson learnt. At least instead of being a total waste of money you will get to travel in PE.

P.S. Please be careful when receiving phone calls / emails suggesting that you have won the lottery, but only need to provide bank details to confirm...