Room only reservations must be paid over the phone, but packages can be paid online. You get a confirmation via e-mail.
It is good not to call at certain times of day; for instance noon to 1 pm in all times zones, because people are taking a lunch break and calling into CRO. Also, if some new discount is offered; the lines will be tied up for hours.
I find mid-morning (EST) or mid-afternoon are the best times to call while most people are working.