Who called from 3124530974

keep getting unwanted calls on my fax number

keep getting unwanted calls on my fax number

This number 1-312-453-0974 cals my house each day and if I answer they claim it's American express... they ask for me and then hang up.
Or they just hang up after I answer. I don't own or want an American express card.

When I repeatedly try to call them back I only get a message that says all lines are busy.

Who the hell is this and what do really they want?

I did not pick up bc I didn't recognize this number.  They didn't leave a message.