You say you've tried everything, so I assume that includes washing the quilt with detergent? Every article I've read on marking a quilt cautions that you try the markers out first on the fabric you intend to use - yet I just used the Bohin chalk on a quilt that I was making without trying it out. Fortunately for me, the marks came out just fine. I think it depends on the fabric, the color of the chalk, the amount of time the chalk has been on the fabric, and possibly on what music was playing while you applied the chalk. I hope you find something that will take out the chalk marks. If you post a picture of the quilt perhaps someone will have another idea for how to remove them.