Return it and get another one, shipping damage should be covered with replacements. If you want to not bother with it and don't care if you ruin it further, try heating it up for a bit with a hair dryer on high to soften the plastic, then get something like a ruler with a thin towel to cover the mouspad so you don't scratch it and push the bent area like you are spreading jam thin, can also heat it up and then put something flat and heavy over it for a few hours or overnight. Actually even if you try that, and contact support and tell them you tried to straighten it they should still replace it.