There is simply beeping on the other end. Perhaps like an old fax beep (but no other fax sounds)?

(Caller Company listed as shown on Caller ID)

I received a call at 4:30 am on my home phone from what appeared to be an incoming fax from NETPROWA...  I called the number back and it asked we to leave my number to be removed from their fax list within 48 hours.   I never signed up to receive faxes from anyone in the first place.

They called my regular #--not my fax machine number and there were just beeps on my answering machine.

Number keeps calling.  This time at 6:39 am Florida Time to my cell phone.  Scammer.  Finally got a person to answer.  When I complained, he hung up on me.  Could hear other people in the back ground when they finally answered.  This number is used for both phone and fax.  He said he did not call me, but funny he answered phone.  Or was it one of the others in the background?