Automatic Renewal Dislike

I didnt appreciate the automatic monthly renewal despite checking days beforehand which didnt allow me to cancel but instead suggested I can simply renew manually when premium account expires (on December 28th). So I figured I dont have to do a thing to cancel since it needed my intervention to buy the In App Purchase ONLY when it expires. On December 29th I checked my account to see that Im now valid until January 28th which I didnt want. How will I prevent this from happening again please?

Merikanova about Todo Cloud: To-Do List & Tasks, v8.0.4