Htc first text messages

[ALEYAHSMAMAW]

How can i delete all of my messages at one time. I'm having to delete them one by one and its getting old pretty fast. I'm talking about the blue message box with an n or it kinda looks like an n in the box. Im not talking about the green box with the smiley face in it. Now, the green box will let me delete all my messages at one time. Please help me. Thank you