I have been using Globalstar and it failing fleet of satellites for many years. I own my own phone and the airtime pricing can't be beat. To help overcome all the deadtime when only faulty satellites are passing overhead Globalstar list on their site the times when a functioning satellite is over the region you have selected. This information is available for about the next two days.

I turn the phone on when my notes say it will work. Each evening when I do this the next batch of call times comes to me via a text message from my wife. She sends me the call times from 6PM to 9PM. There would always be at least 3 call times of about 10 minutes duration. I would also call her each evening and check in. Using this method I was never wasting battery power. I was able to call her most nights and talk for a few minutes. Twenty three days of this and my Globalstar phone still showed half of the battery power remaining.

It was a bit of a hassle but it worked well for us. If you can pick up a used phone cheap and get their unlimited package of text and talk it might be an option.