Yes, I found out later that I was M, sorry for not having said that earlier.
Looking at the Flight Attendant's screen, an upgrade to Economy Premium would have costed me 25k miles.
If moving from M "should" have costed me 25k, that 45k price (even with a 10% discount, if I was right to claim it) becomes a rip-off. Then, I had no way from the website or the app to upgrade to Business before departure, so i'll try and ask by phone next time. 25k would have been worth it for sure - I might have had a better sleep.
Thank you all for your answers !
