In the past two days alone, I've gotten over 20 spam calls with none of them leaving a message. Just 3/4 seconds of silence on my voice mail. One call the other day left a 22 second blank message.
Yep, I got a series of those recently claiming that I had unpaid paid tolls. Each messagr came through as a group text with two or three random numbers, which were immediately removed from the group after the text arrived. I've been wondering why they started doing this. I assume they're trying to exploit some kind of loophole in the carriers spam filtering.