How do I cancel? – Invitation Maker - Flyer Maker Review

I signed up for the free trial... then went back and actually read it and the fee is $49.99 a YEAR?! I’m still in free trial mode but want nothing to do with this app? How do I ensure I don’t get charged through my iTunes account?! I need to know ASAP!
Review by Ksasa808 on Invitation Maker - Flyer Maker.