Plan credits lapse at the end of each paid period; top-up credits never expire (Terms §8.2).
The button below opens secure billing management — cancel there in two clicks, online, immediately, no phone calls, no hoops. Cancelling stops future charges; you keep access and remaining plan credits through the period you've paid for. You can also update your payment method and see invoices.
Your subscription is billed by Google Play, so Google manages cancellation: open Google Play → Payments & subscriptions → Subscriptions → Nonchalant → Cancel.