The reason why you got 2 charges in your card is that it was declined on our first payment gateway due to some missmatch in billing address with the info that you have on file with your bank. Another charge (second one) was approved. But the problem is that the fist charge is not a charge. It's just pre-authorization that will be cancelled automatically within few days.
If you wish to have the first charge to be cancelled faster you will need to call your credit card company (the number to call should be at the back of their card) to ask them to release the pre-authorization right now or else they will have to wait for 3 to 7 business days.
Please do not cancel second charge. Otherwise we will not be able to ship your order.