For my work I use sat phones. The Globalstar is so worthless that we junked them. The Iridium works fine. Globalstar failed to shield their electronics on their satellites from solar radiation and they were destroyed, unrepairable. The Iridium phones work good but there's a catch; to place a call, you hit the # sign and hold it until a + shows in the display. Then you can dial a phone # including the area code, etc. For someone to make a call to you, they have to call a special # that rings the earth station in Arizona I think. Once that phone answers, it will prompt you for the phone # of the Iridium sat phone you are trying to reach. Each Iridium phone has an 8 digit # that is not direct-dial, you must dial through the earth station's phone #. This takes time. It's not fast to place a call TO an Iridium sat phone. Once the call is connected, the sat phone users sounds to the landline user like he's drunk or something. The speech is slurred, delayed, stretched out or what ever makes a drunk sound drunk. Every time I make a sat phone call, first thing I tell the party I'm talking to is that I'm on a sat phone and that my voice might sound strange. If I don't, they question me about it. The coverage of the Iridium sat phone is very good. I can be in some pretty steep canyons and it still works. However if I'm under any kind of cover, even in a car, it won't work. Even a carport cover will block the signal. It is truly Line-of-Sight coverage.
BTW, we have our sat phone contracts at very reasonable costs; about $40 a month plus $1 per minute. When you consider the versatility of being almost anywhere on the planet and calling anywhere else in the world, it's pretty amazing and pretty affordable. The phones are not cheap however. I think we paid somewhere around $1200 for a phone with accessories and a Pelican Case and a solar charger for it.
Again, the Globalstar phones had too many times we could not get any bars to make a call and then calls would drop if longer than 2 or 3 minutes. Unacceptable in our line of work.