Pieter If you have 1 personal account, you're paying for 1 personal membership. And if you have 2 business accounts for two different business entities, you're also paying for 2 business memberships. If you just have one business entity, but 2 bank accounts (also called sub-accounts or monetary accounts here at bunq), then you're only paying for 1 business membership (as you can open up to 25 sub-accounts for no extra costs inside of every membership).
Does that make it clearer? If you want to avoid paying for one of these memberships, you would have to close them or in case of the personal membership, you also have the option of changing to the Travel plan, which has no associated monthly costs (but also less features). There is no Business membership without monthly costs, so every distinct business entity for which you open a new bunq Business account will lead to some additional monthly costs.
If something is unclear, just look at the "My membership" section inside your app to see what kind of memberships you have.