i'm gonna tell u something to try i can't guarentee that it will work. but i use to do it make my pleats stay nice crisp. u'll need IRON on STEAM wash cloth. wet but not dripping u lay the cloth on the pleat put the steam iron on top let it lay on it for a few then move it. Re-damped the wash cloth continue. It should work as long as the shirt is clean. that way the creases won't leave dirt crease marks.
Permanent pleats in polyester is quite permanent. You might soften them up but not get rid of the lines.
