Repeated calls to my cell phone daily from this number.  No-one every on the other end when answered.  Trying to return the call results in a telco message that the number is not a working number.  

Call to AT&T customer service results in the same info - and supposedly have no clue how I could receive calls from a non-working number. AT&T wants to charge me $4.99 per month to block calls from this number (scam?).