We claim the ornamental design for a case for a mobile communications device, as shown and described.
FIG. 1 is a front, left-side, and top perspective view of a case for a mobile communications device according to the present design.
FIG. 2 is a back, right-side, and bottom perspective view thereof.
FIG. 3 is a back elevational view thereof.
FIG. 4 is a front elevational view thereof.
FIG. 5 is a left-side elevational view thereof.
FIG. 6 is a right-side elevational view thereof.
FIG. 7 is a top plan view thereof; and,
FIG. 8 is a bottom plan view thereof.
The broken lines depicting portions of a mobile communications device represent environmental subject matter that forms no part of the claimed design. The broken line features on the side surfaces of the article represent portions of the case for a mobile communications device that form no part of the claimed design.