Cannot unsubscribe

i wish to cancel my subscription before my trial ends so i am not charged the $59.0 however I have followed the links from the email and gone to my settings on my Prezi account but there is no section titled "your purchases" and therefore i am unable to click unsubscribe. 

can you please help me unsubscribe before my trial is up on the 26th July so that i am not charged the $59.0