Upgrade supports pack can't be done when bought trough steam ?

Dear support,

I do enjoy your game a fair bit and want to support you guys.

I started with the basic pack but now i want to upgrade to the next level.

Now i followed your post on how to (go to account, transactions, etc)... but i can't find annything under transactions.

Is this cause i bought it trough steam ?

I assume if you want to upgrade your pack you don't have to pay full price for the next pack ? just the surplus ?

Waiting for your feedback.