My mon is in NA and has been getting the same calls!  I called for and blocked the number for her and it stopped for 3 days and she just told me it started again today.  Th caller ID says Hackensack but then on Reverse lookup I found it is a landline with an MCI carrier and it said Newark.  I am wondering if it is coming from a Jail in Bergen/Essex County???  I had trouble with that a few years ago when I lived in Jersey City.
I do find some common thread here, my mom had her house up for sale last year.  Coincidence???  Someone has to get to the bottom of this and I won;t stop till it happens....Good luck everyone!

The call comes in at random times from this number.  As above poster stated.  It just says in a very eerie robotic voice.  "Hello.  This is a test.  Goodbye."  It's bizzare.

Not sure who your carrier is, but I have Verizon and called to report this issue.  They gave me the number for their "Unlawful Call Center."  It is 800-518-5507.  They're closed now, but I'm going to call back tomorrow.  Their hours are 8:30 a.m. to 5:00 p.m.  Hope this information helps.

I get that too, started out of the blue... The robotic voice "Hello, this is a test. Goodbye.". If you answer it, no robotic voice just silence. I'd suspect its probably some telemarketing firm fine tuning their electronic delivery system and records?

I reported it to Verizon and traced the call.  According to Verizon, they are working on it.  However the calls are continuing and now it's a person's voice saying. "Hi.  It's me.  Happy Fourth of July."  This is some sick individual.