Has called twice, no one answers when we pick up

I keep getting phone calls from this number. When I pick up, no one is there. If I let the call roll to Voicemail it'll record nothing for 10 seconds and hang up. I've tried calling this number back and I just get a Voicemail message saying the mailbox us full. This number calls at least three times a day and I'm tired if it. Anyone else have the same issue?

Just received a call from this "cell phone" number.  I usually don't answer callers whom I don't recognize but since it said it was a cell phone caller, I wasn't sure if it would be someone I know.  They took about 10 seconds to respond to my "hello" and then asked for me by name.  They said they have heard reports from people in my neighborhood having bad water and basically wanted to know if they could test out my water.  I just said "no thank you, I'm not interested" and hung up.  And btw, our water is perfectly fine.

I received a phone call from this number, and agree, they don't come to the phone right away..I use the "block" on my phone, so I don't know how this number gets through...I'll remember this number, and won't answer it again.