800-457-5437 is always calling my fax machine. Normally at the same time they call the business voice line at the same time the fax machine is ringing. Sometimes they try to say they are from Discover Merchant account phishing for information. Other times I can't even understand them at all because it is a lady the don't speak english very well. Then sometimes a guy will call speaking english with a mid country USA accent.

Pretty much always phishing for information and then hits you with a sales pitch. If you answer they will just start talking asking if you are the person listed for the phone number and then trying to gain information. Never the same thing always something new.

I found that If I just answer the phone and put it on speaker and not say anything that I can keep them on the phone talking saying things like I can hear them in the background and talking to someone else with them. My longest time of playing with them has been just over 5 minutes. They will talk to a speaker phone without me talking back for the longest 1.5 minutes before they hang up.

have some fun with them they are people too so may as well try to sell them something.

Called my number, as well.  They left no message.

Called my cell phone, didn't leave a message