I tried to extend my booking online but there was no option to do this. I wrote to the helpdesk to ask how to do it and they sent me instruction to do it online, but they didn't work as the option to extend online didn't exsist. As a resuly of not being able to get a clear instruction on how to do it, I had to pay an overstay charge which was far more then had I been able to extend. I wouldn't recommend using this service if there's a chance you need to stay longer, or your flight gets delayed. The make it very difficult/impossible to extend before your oriignal booking expires. Very poor service and communication.