Yes, depending on a few items you can either cancel your trade yourself or you may have to contact support.
If your payment has not been completed (ie it does not show settled in your transactions tab) and/or the property is not yet fully funded, then you can select the trade in the transactions tab and there should be a cancel button. That cancel button will null the trade and if the payment has initiated then the system will refund your payment.
If the payment has been completed and the property is already fully funded, then you will need to email us at firstname.lastname@example.org so that we can look into cancelling the trade for you. We are not able to guarantee a cancellation due to the items above.