Plans aren't switched with a self-service toggle on the Billing page itself - there's no "change plan" button there. Instead, Sprwt shows an upgrade screen whenever you open a page that needs a higher plan than you're currently on (for example several Business Intelligence reports that require at least the Bloom/Base tier):

1. Open the gated feature; Sprwt shows a plan-comparison screen listing the available tiers (Seed, Sprout/Starter, Bloom/Base, Orchard/Pro) with their features and pricing.
2. Click Subscribe on the plan you want.
3. In the Request Plan Upgrade window, click Submit request - this emails Sprwt support with your request.
4. Support upgrades your account on Sprwt's billing account; the new Plan row and amount then appear on Settings > Billing.

You can also reach support directly, or through Support > Addons, to ask about a plan change. Features gated by plan tier or by purchased modules unlock as soon as the account is updated.