Come faccio a passare dal piano Personal a quello Business?

You cannot upgrade the plan on Tilda. However, you can switch to a Business plan before the Personal plan expires. To do this, it is enough to pay for 1 month of a Business plan on the Plans and BIlling page in your account. Unused days of your previous subscription will be accumulated and recalculated automatically.

If you are a Business plan subscriber already but you need more than 5 websites, you can switch to any Business plan on the Plans and BIlling page as well: Tilda Business 10, 15, 20, 30, or 40. The paid subscription period will be recalculated automatically.

Per saperne di più su Prezzi e pagamenti: http://help.tilda.ws/subscription#personaltobusiness