Rule about the payment to aankoopmakelaar

In June 2020 I met an aankoopmakelaar to get help for buying a house. We never had any contract signed as it was on basis of no cure no pay. In 2020 he mentioned in case of success he will ask me 1800 euros including VAT. I have a screenshot of his website about this tariff in 2020. In Nov 2020 we found a house and signed the purchase agreement,etc together and it stayed silent till May 2021 when I had to get the keys at Notaris and became an owner officially.

Since Jan 2021 my aankoopmakelaar has increased his tariff from 1800 to 2400 euros for people. My question is: does he have any right to charge me 2400 euros suddenly just because the transfer date at notaris has happened in 2021?
I hope not because he did all the works in 2020 with 1800 euros verbal agreement. Thanks