Plan change timing
- Yearly to monthly, or yearly to a cheaper yearly plan: the new plan is deferred to the end of the current billing period. The current plan is kept until then.
- Monthly to yearly: the new plan is applied at once. The store is billed for the full year and credited for the unused days of the month.
- Any other change is applied at once. On an upgrade, the store is billed for the price difference over the days left in the period. On a downgrade, the store is credited for the price difference over the days left. On a change to the same price, the current period end is kept.