This is the toll free pumper scam. calls your 800 # Friday thru Sunday filling up your business voicemail so they can collect the connection fee. Calls from a different # each day so cant be blocked.  Collects about $10/month in fees from 10-20 thousand small business owners. Not a bad take for thieves with a robocaller. The message 'you are the first caller on the conference call'. hang up immediately- each extra minute costs you.