800 531 5000 is owned by Direct TV call center / AT&T which is a telecommunication company. AT&T/DirecTV company is using this phone number for support and promotion of their services. If you are the customer of Direct TV or AT&T then you will always receive calls from this number. 800-531 5000 phone number is toll free so if you are willing to get help from customer support then you will not be charged.
Finally: It is safe to answer calls from 800-531 5000 telephone number.