I use IridiumGO. It's a satellite transceiver that uses a WiFi Hotspot setup to connects to your existing smartphone. The equipment is about $1,000 as I have it but that's with a fixed rooftop antenna, docking station, and portable non-hotspot kit as well. If you just do portable, the kits can be had for as low as $500 or so. The nice thing is you can still use your smartphone as the handset (no need for any second satellite handset) so you have all your stuff right with you. The hotspot device can also be used in a portable mode so you can take it with you as you hike away from the RV and still have full communications with the portable antenna.
The monthly plans is where you need to be careful. I have a full plan for $125 a month. This gives me about 3 hours of full talk time along with unlimited messaging/texting and unlimited data use. Now many will think why not use an internet based phone service and get all the calls free? Well the satellite internet does have latency issues which makes normal conversation buggy at best. The voice minutes is immediate.
There are other satellite services, but my main concern was being able to use my smartphone instead of carrying two handsets. And since it's a hotspot, I can also use my laptop on the same system. The added portability of the entire hotspot made it a winner in my book.
And to add, the nice thing is you have the option on your smartphone of using satellite (with portable kit) when no cell service is available or using cell service if it's available.