The free trial
New accounts get 7 days of Pro with no card needed. When it ends you keep the free version unless you choose Pro.
Pro
Pro is $9.99 a month or $59.99 a year in US dollars, or the equivalent shown in your App Store region. It is billed by Apple to your Apple account.
Renewal
Subscriptions renew automatically until cancelled at least 24 hours before the end of the current period.
Cancelling
In your iPhone: Settings, your name, Subscriptions, Life OS. You keep Pro until the end of the period you paid for.
Refunds
Refunds are handled by Apple at reportaproblem.apple.com.