The ornamental design for a necklacecharm, as shown and described.
FIG. 1 is a perspective view of a necklace charm;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a right-side elevational view thereof;
FIG. 5 is a left-side elevational view thereof;
FIG. 6 is a bottom plan view thereof; and,
FIG. 7 is a top plan view thereof.
The broken lines shown on the drawings are for purposes of illustrating unclaimed portions of the necklace charm and environment and form no part of the claimed design.