In principle you can change the appointments prior notice before the time of the take but the conditions of cancellation of the same are as follows:

If the cancellation occurs at least 24 hours in advance, we will send you a full refund of the trial except 5€ management.
In the event that it is not notified before 24 hours of the appointment to cancel or change the appointment before and does not appear at the agreed place at the time of the appointment, the user will lose all right to claim returns or to demand any kind of compensation.
To communicate a cancellation or change of appointment it is necessary to contact citas@ealaboratorios.com .

If you are out of business hours, you must send an email to citas@ealaboratorios.com in advance of the appointment for confirmation.