The ornamental design for a cellphonecover, as shown and described.
FIG. 1 is a front view of the cell phone cover showing my new design;
FIG. 2 is a rear view thereof;
FIG. 3 is a right side view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a top view thereof;
FIG. 6 is a bottom view thereof; and,
FIG. 7 is a front perspective view of thereof.
The dot-dash broken lines represent a boundary of the claimed design. The dash-dash broken lines depict environmental subject matter. The broken lines form no part of the claimed design.