My wife has complained to me a couple of times lately that calls are not completing. No ring, just silence for a few seconds, then you get an operator voice, "Goodbye." WTH

I just had it happen placing a call to 831 area code. Other calls seem to be ok, but every time we call that number (over the last 20 minutes or so), this problem occurs. My wife said it's been happening randomly otherwise. Any ideas as I dodge frying pans?