I have a skytel pager but it must not be satalite because reception is very spotty, I've ask my office many times if they can just pay part of my cell phone bill since I miss so many pages.
Sept 11, 2001 so far has been the only day my verizon cell phone has been unable to call and even then it was a fast busy as all the circuits were tied up.
Text messaging was the most reliable on that day since it takes very little bandwidth to get the message through so after a few retries the messages would squeeze through. We went and upgraded phones shortly afterward to get text messaging capability so its there if we need it. Other text services such as blackberry were still working as well.
Cell phone and land line companies have high uptime SLA's they must meet and even have mobile generator trucks which will drive around to each tower and charge the batteries as part of their DR plans.