MANY low-priced $99 lenses today are "loose" and sloppy-feeling in some way. Wobbly...seriously...I own or have owned some Nikon zooms that had wobbly front sections, BY DESIGN, and which shot great. it is unnerving, however....and frankly I do not quite understand how it can work, but it does.
So...do you mean the zoom slips or creeps? Zoom creep is one term commonly used.
What, exactly, is the problem? What do you mean by loose zoom? Wobble? Or zoom creep?
Are the pictures coming out alright? Or is the problem actually affecting the image quality?
Generally, people do not repair the 18-55 zoom, but instead, buy another one to replace a damaged or defective one. Used examples are often very affordable, and camera repair charges often make it more-economical to replace defective gear, rather than repair it.