Can I switch plans?
There is one plan today — Lonzo Agenda — so there is nothing to switch between. The second plan, Lonzo Assistant, is coming soon and cannot be subscribed to yet. Tapping Manage plan in Lonzo still takes you to Google Play, where your subscription is billed, to cancel or to update your payment method.
When the second plan launches, moving between the two will be a plan change on your existing subscription rather than a cancel-and-resubscribe, with Google Play handling the pricing adjustment. Nothing will be re-provisioned: your Google connection, your classified mail, and your Agenda carry forward either way, and moving back down will delete nothing — the capabilities simply stop being available. See the Subscription & Billing Terms for the specifics.
See also: How do I cancel my subscription? · How do I export my data?