That's right about how people do cancel appointments. Also they can move appointments to accommodate urgent need situations. They did it for my son when he had an appointment two weeks away and moved him up to from a Friday to the following Monday. Later there were times when the office would call me to see if my son would agree to a later appointment so someone else could get in earlier. It's always a good idea to be polite and nice to the office personnel and especially the nurses who can help you. Remembering their names is good, too so you can know who said what and refer to it.