First if bill avilabile then check itPls buy 2 to 6 months used mobiles onlyCheck all tests mobile if avilabileFirst see screws of any mobile if mobile screw is ruff then dont buy it not seald its opendCheck imei number on mobile and bill if new mobilePls prefer brand mobiles like mi nokia samsung lg sony htc etc.Last word dont buy only single person pls go with any tech student or friend because reason he no some you know some help full u