I would return it, even if it has been cut. To my way of thinking it is defective and the store and the manufacturer should stand behind what they sell. If they don't, I guess they don't need my money. If the retail shop won't refund your money, contact customer service at the manufacturer directly and kindly explain what methods you have tried to get it to flatten, and that the retailer would not replace or issue credit for what is clearly a defective product. Ask them if they would issue a pre-paid shipping label so that you can return it to them so they will know what you are complaining about. Most of the time, they will either replace it or give you a substitute. I worked with customer service for many years and the key is to keep cool and calm and make them feel sorry for your inconvenience. If all that fails, tell everyone you know what happened so they don't buy that product or deal with that retailer. Also, write a bad review on any site that sells that product. Sometimes the only way businesses understand is if it will affect their bottom line.