I'm currently in a 48 hours stopover in Europe ... I just learned that you can't ask for an upgrade for the next flight (from Frankfurt) even in 2 days because I already used part of the ticket ...

This was not what I was told the other day, they told me to call the day before, now it's too late.

Also I'm willing to pay extra for the difference in fare to upgrade but because I'm on a stopover it's not possible?! Can someone confirm ?