It worked quite nicely as an extra business accoun...

It worked quite nicely as an extra business account (no costs in addition to the transactions / account statements you asked for), then they send you an e-mail that you are transferring to another variant due to a renewed business package. Nowhere is it clearly stated that you are now suddenly going to pay, the only thing that could indicate this is the 4th paragraph which states the following statement:
Today you can take advantage of this and many other features that save your time, for just 9.99 / month.
I have never seen this, in the chat I get the reaction that I have read it. This confirms mailchimp.
For a bank that says it is minded this is of course a joke, opening an url in the email equals reading.
If you are going to adjust prices unilaterally in this order of magnitude, ask for a read confirmation / agreement.
Instead of deliberately communicating unclear about the upcoming costs, and not wanting to apply a settlement when it is established.
Hopefully my second account with ING will be opened soon so that I can say goodbye to this bank.