We claim the ornamental design for a mobile phone case, as shown and described.
FIG. 1 is a front, left-side, and top perspective view of a mobile phone case showing our new design.
FIG. 2 is a front view of the mobile phone case of FIG. 1.
FIG. 3 is a rear view of the mobile phone case of FIG. 1.
FIG. 4 is a left side view of the mobile phone case of FIG. 1.
FIG. 5 is a right side view of the mobile phone case of FIG. 1.
FIG. 6 is a top view of the mobile phone case of FIG. 1; and,
FIG. 7 is a bottom view of the mobile phone case of FIG. 1.
The broken lines in the drawing figures form no part of the claimed design and depict portions of the mobile phone case that form no part of the claimed design.