As per Iberostar's cancellation policy, you are presented with the Pay at the Hotel Rate, which allows you to freely go about things without worrying about some situations. This is because this method makes it easier to cancel your booking in case an emergency occurs and you cannot make it to your vacation.
Canceling your booking will cost you nothing as it is free, and you have up to four days prior to your hotel check-in to cancel it. If you cancel your booking one day before your arrival, the cancellation will incur an $18 charge; this also applies to those who might cancel in less than four days from when the hotel is expecting you.
The process requires you to contact customer service and handle the whole process with them. Reviews from previous customers show that the cancellation does work out, as some have successfully canceled without paying any fee.