All Series 3 Memberships have a minimum commitment of 6 months, unless a longer term is purchased, in which case the membership commitment period is equal to the length of the plan selected.
For full commitment terms, see: Terms of Service
There is a 30-day trial period for all Series 3 Memberships, and returns can be made during this period. See: What is the Fi Subscription/Membership Trial Period?
When making changes outside of a return period, the changes will take effect the following billing period. See: How Do I Update or Cancel My Fi Subscription/Membership?