I was mad how there was no account setting in the app but I never gave up on looking on a way to cancel my subscription. All you had to do was go on a Mac or PC and download iTunes. Login to your account and then click account then click view my account scroll all the way down and it should say settings and it would say your subscription manage and then cancel your subscription and there you go hope I help everyone who is in need.
AlienB0$$ about Yarn - Chat & Text Stories, v1.6.0