Goliathus Extended Chroma Creases Help!

I bought a goliathus extended chroma a couple of months ago and it is brilliant but recently the mat has developed a lot of creases. After following all the official guidelines for flattening the mat it just does not want to go back to its original nearly flat shape that it was when I received it and it is now affecting how I can use the mat as the bumps affect my mouse movement. Whats my best course of action? Thanks for any help.