If the purchase has been made via Saronic Ferries online booking, you should send an email to  customer@sf.gr or contact us or visit  the port offices up to one hour prior to the scheduled departure time.
If the purchase has been made through any other online ticket agency or a physical ticket office, you must contact the respective issuing agent, or visit  the port offices up to one hour prior to the scheduled departure time.
Your open date ticket can be used for travel up to one year from the issuance date.