When Legacy Type movement is enabled, the camera will automatically turn based on the direction your character is moving or facing.

If you would like to disable this automatic movement, from the main menu, select System and open the Character Configuration menu, then select the Control Settings tab from the column on the left. Under Movement Settings, highlight the "Disable camera pivot." box.

When the "Disable camera pivot." box is highlighted, your camera will no longer turn automatically and will face the same direction until you choose to adjust it. If you're not quite sure which one you'd prefer, try moving your character left and right a few times, once with camera pivot enabled, and once with it disabled, to see which option works best for you.