Tell me about it. Last week, I was in Big Bend NatPk. I wanted to ride my enduro bike up a 30 mile 4wd road, solo. My friend agreed to be "support crew" and both of our phones showed at least 3 bars of service. I texted him a dozen times as I progressed, all good, ride going well. The agreement was that if I didn't show up in camp at sundown, to start a search. Me, thinking all was well, kept riding, extending the ride to over 100 miles. I then get a text saying "ET phone home, it's been over 3 hours!" I hightailed it back to camp just in time.
He didn't get my texts until the next day!!!

I had ham radio with me but still couldn't get a phone call through.