No, the data from the notification portal cannot be deleted in this case. Your data is in the notification portal because you are legally required to be registered as a service recipient in the notification portal, pursuant to the monitoring provisions in the Employment Conditions of Posted Workers in the European Union Act (WagwEU). Your data will be stored for up to 7 years, and then deleted.
If there is another notification about an ongoing posting, you are no longer the service recipient and you are not a client for this company or service, you can contact the Netherlands Labour Authority (email: contact@nlarbeidsinspectie.nl, telephone: 070-3336728)