How do I cancel the premium subscription?

Tariq's premium subscription is managed from your Apple account, not inside the app itself. Open your iPhone Settings, tap your name, then “Subscriptions”, and select Tariq.

From that screen you can change plan or cancel the subscription. To avoid automatic renewal, cancel at least 24 hours before the end of the current period.

Cancellation takes effect at the end of the period you've already paid for: you keep premium access until then.