The WS-C2960-24LT-L has 8 PoE ports, are these specific ports or can you have any of the ports support PoE, up to 8 @ 15W? Can you have 16 at 7W?
Look at the switch. If you notice the first 8-ports have a white line around them with the letters "PoE".
The first 8 ports are the PoE ports and provide upto 15W per port. This is fixed and you cannot provide PoE to additional devices