Moritz With a 3 months notice, they may have been able to - but they actually promised it’d be free for as long as you like. That was a lie. Now of course the solution is: claim breach of contract and... leave. That’s the position bunq is taking. They know you only have one choice: pay up or claim its a breach and undo the agreement, ending your account.
... However, given the impact of a bank account and the promises bunq made - if you were to challenge this in a smalls claims court (possible on EU-level), I wonder if this argument would hold up. I doubt it would. But really, who’ll do that? Bunq knows they have you by the... Well, you know. ;) And this arrogance when dealing with clients is what will eventually destroy bunq as this is the Xth time they violate their customers’ trust and break promises. You can’t rely on what they say, they’ll change it at will whenever they please and don’t care at all if they lose you as a client because of it or if it hurts their name and reliability. Its all about the money and data. :)