Subscriptions are billed by Apple or Google, so you cancel or ask for a refund with them. Deleting the app or your account does not cancel your subscription.
If you pay for Premium, open the app's menu and tap Unlocked! to see and manage your subscription. If someone else on your account pays, only they can cancel it.
See Cancel a subscription from Apple.
See Cancel, pause, or change a subscription on Google Play.
You keep Premium until the end of the period you paid for. To avoid being charged after a free trial, cancel before the trial ends.
When the period ends, you keep everything you logged, and nothing is deleted. The people on your account stay on it, and lose the Premium features they had through your plan. If you subscribe again later, everyone gets Premium back right away.
Apple decides on refunds for App Store purchases, and we can't refund them for you.