The ornamental design for a petcollartag, as shown in the accompanying drawings, and as described.
FIG. 1 is an isometric view of the inventively ornamentally designed pet collar tag; and,
FIG. 2 is a reverse view of the inventively ornamentally designed pet collar tag. Dashed lines appearing upon the view are intended as representative of text and are not considered to constitute a part of the pet collar tag.