I'm not a lawyer. I'm writing here to give you first support and I hope someone with proper knowledge will help you. Please do not take this answer as final.
First, during my living in the Netherlands, I found that Dutch are operating a lot with common sense. The law is trying to protect the weakest party, which in this situation you are.
I don't know you personally, so I treat you from what I read. I also treat agency based the on text from the previous topic. As for me, they don't play well.
Yes, you had a verbal agreement but I think for such types of contracts Dutch law prefers the written and signed contract. I don't have details of your verbal communication, but it sounds reasonable that you decided to stop with it as you got all details of the contract. I also found a link which gives me hope that I'm right.
If you're not sure then pay 200 euro for a layer and get the proper answer. Ironic that I do remember that you wanted to save them.
In the worst case, you can sign and live in the apartment no longer than notice period in the contract.
I would also advise you to get legal insurance. However, it will not help in this case.