Yes, you can modify it, but under certain conditions.
Firstly, you need to verify that the booking is not in penalty. To do so, we recommend you to check the paragraph "Cancellation Terms" on the confirmation email you received.
If it is in penalty, it will not be possible to make any kind of change. If it is not in penalty, you can send a request through the appropriate form "Request Assistance" that you can find in your Reserved area of our site by selecting as a reason "Change Booking".
The office will answer you within 24/48 hours (during office hours, excluding Saturday afternoon, Sunday and holidays) informing you of the possibility to make this change and if there are any surcharges to be paid.