If you upgrade your profile from the Standard tier to the Enhanced tier midway through your payment interval, you will be automatically charged a pro-rated amount for the upgrade (prorated from your initial upgrade date).
If you downgrade your profile from the Enhanced tier to the Standard tier midway through your payment interval, a credit will exist on your account through our third party payment processing system. This credit will be applied to future automatic payments. A refund will be issued if you switch to the Free tier and a credit exists.
Note, payments / subscriptions made through Apple's interface can only be managed from there (vs. on FPF's app or website). Please contact Apple Support (https://support.apple.com/billing) with any questions regarding payments and refunds.