You can file your complaint online for issues within the jurisdiction of the Hellenic Data Protection Authority (HDPA), for violations of the legislation concerning for example:

• the rights of the data subject provided for in articles 15 to 22 of the General Data Protection Regulation 
• sending junk emails and in particular spam emails or sms.
• telephone calls to promote products or services and general promotional purposes
• use of the Schengen, Visa Information System (VIS), Eurodac and EKANA systems

You will need to login with your personal Taxisnet credentials.