Calling and using the website will generally accomplish the same thing. If the site is down (which has been a lot as of late), you might be able to reserve on the phone, and then again you might not, depending if the CM is also locked out of the system.
I always use the website and have good luck with it. It's my understanding that as long as the website is working properly it is showing the same available reservations that the CMs on the phone can access.
Just keep checking multiple times a day. It does pay off. Good luck!