Something that may not be clear. Online reservations are different from phone made ones. I had multiple reservations made online (as the days we wanted became available), there was no way to just add days to an existing reservation online.
When I called about combining them, it was quite a task. They actually cancelled my online reservations and made fresh ones. ("What if you couldn't have made fresh ones?", "Gee, I guess you could have lost your reservations"!!) At least that's how it was handled, in the end, most recently.
Once my reservations were combined, I could no longer see them online. I was told they were in a different system now.
I can say that the folks on the other end of the phone were willing to do whatever I needed. A lesser organization would have sent me packing...