866-673-3916

Who are they?  Phone number shows up on a cellphone I rarely use.  No messages are ever left.

Me too. All they do is hang up and my answering machine records the hanging tone.
I am now using the following trick: as soon as it comes on, I pick up and just lay the receiver aside until I hear the "hang up" sound. They have to pay for the connection until they decide to hang up...

This number calls and constantly hangs up.
This is a deliberate act to give you high blood pressure.

this number calls my cell several times a day but never leaves a message! Its really irritating and no one
seems to know who they are.

i keep getting calls several times a day from this number.866-673-3916. The people never leave a message and after i have asked them OVER twenty times to leave me alone they still continue to call. plus my husband and i have called them back and asked to speak to their so called supervisor and we have been told they either dont have one or they all are in charge. the chic cussed me and my husband out after we told her to stop calling. they called one day 16 times! who does that? pleas does anyone know how to stop these people? they are a scam and claim to be a debt collection agency. i shouldnt have to change my number becuase these people are physco!

All I know to do is put on the "Do Not Call Registry," online, and if that does't work, report them to the Attorney General's Office.

They are a medical research company. I signed up a couple of weeks ago and this was the return phone call.