These are spammers. Walmart will refer you to an attorney because they are using Walmarts name.
You can call them, but then they want the number to cancel and they will just add you to the list.
So, call them a lot and tell them how you feel in a careful and controlled way before they hang up.
Got some more info.. A friend from Sprint helped me find out something. All area codes (NPA) and prefixes (NXX) are owned by specific carriers and then are assigned to a business, home, etc...
The NPA 856 and NXX 295 is owned by an suspicious phone company out of Chicago :
http://www.peerlessnetwork.com/
They can tell who owns all these numbers and we should all call them.