They let the number ring until the answering machine comes on and then they immediately hang up. I don't answer any number that I don't recognize. They even called on Sunday morning. That takes a lot of nerve.
They called and repeated hello six or seven times. No introduction as to who they were. I will NEVER answer a phone call that will not identify themselves first.
Caller ID says "Dallas TX." Called home landline at almost 8 PM. We let voice mail answer. After recorded greeting a male voice came on. He spoke twice: It seemed like "Hi? Hi?" or perhaps a poorly pronounced "Hello? Hello?" Then hung up.