Can you upgrade Universal One Day passes?

[erinch]

Does anyone know if you can upgrade Universal passes?

We have 4 1 day universal passes-the one which doesn't expire till 2030, and is good for either park. Universal supplied them after causing a food allergy reaction (different story) which ruined a day (and a trip). We didn't use them then, because Universal ended up doing better than that. This year we're planning to get the 5 park flex pass, and I was wondering if the one day passes could be upgraded to the flex passes?

 

[MO Disney cruiser]

I would think yes. I called them last week to ask if I could upgrade my 3 day pass to an AP and they indicated it was no problem. Just have to pay the difference.