Selvedges shrink a lot (which is why we never use them in quiltmaking). Try snipping through the selvedge every 6-12" and see if the piece will lie flatter. When I remember, I do it before laundering, but I usually forget and have to do it afterward. It's much more noticeable in a longer yardage.
Remember that your cut edges won't line up - don't worry about them. Hold both selvedges in your fingers and shift them until the fold falls straight below, as if you are folding a bed sheet.
BTW - I wouldn't always blame the cutter for crooked edges. When I worked at quilt stores, we were often irritated by how poorly the "top quality" fabrics were wound on the bolts.