How to cancel dog pal before 3 day trial

Cancel a trial the same way as a paid subscription. There is an Apple article that explains how to cancel subscriptions. Click on the following link: If you want to cancel a subscription from Apple - Apple Support

I’m trying to cancel dog pal app before the 3 day free trial is up but it won’t let me. When I hit the red cancel subscription it just turns black like it will cancel then becomes red again & it is still listed as a subscription. It will not cancel! I just downloaded this morning is that why? I will wait til tomw & see if it’ll cancel then. I do not want to be charged $19.99 for this app!