Who called from 2151881200

I received three missed calls from this number and when I called back it said not in service. Does anyone know what it is

These are Electric Suppliers Hawking for Business.  They call from different numbers. Another one of their numbers is 215-188-5400.  Report EVERY call to the Do Not Call Complaint form.......

These Electric Suppliers never give up!  They have called me 9 times.  I don't even have electric bills to pay.
They are the worst offenders.  The times I accidentally answered the phone, they say they have  an
important message about my electric bill.  I immediately hang up.