How to change to an All Apps plan when I already have 2 other active plans?

Hello!

I have a fully pre-paid annual student Photography Plan (Ps, Lightroom, Bridge) that will be active until 19/06/2019, and also another fully pre-paid annual 1 App Plan (Illustrator) that will last until 31/10/2019.

Now I want to upgrade my subscription to an annual All Apps student plan.

How should I go about this?

Should I cancel my Photography and Illustrator plan first before getting the All Apps plan?

But if I cancel those two plans, would I get a refund for the spare months that I didn't use?

Or will the All Apps price be somehow recalculated to accommodate the the 2 months of Ps,Lr,Br and 4 months of Ai that I'm still entitled to?

I'm still a student so even if this is a month issue, it's still a big deal for me since I don't want to over charge my dad's credit card.

When I enter my account and go to My Plans and then click on Manage, the options available seem to be for other issues or to completely cancel the plan. I don't want to do any blind cancelling until I have this figured out.

So, thank you in advance, I'll appreciate any guidance on this matter

Antonella.