How can I cancel the subscription? – Bloomz: For Teachers & Schools Review

Our K teacher asked us to use the app for convenience, so I bought a 1 year subscription. I’m not using the app since last August, but there’s no option to cancel the subscription - neither in Apple Store, nor in the application. Am I supposed to pay the 9.99 forever?
Review by vm0720 on Bloomz: For Teachers & Schools.