Bought an item ( tankless water heater) on Amazon, opened it to find that materials used to make the item can cause cancer and birth defects. I decided I don't want my young daughters near this (installation in bathroom). Made my concerns known to Amazon. They credited my American Express for the full amount, but the company which actually shipped the item refuses a return because it was opened (but not installed or defaced in any way). Does Amazon have the option of rescinding the refund?