Squarespace Scheduling is a separate product and is not included in any website plan. You must pay for this separately. See the scheduling pricing further down this page
If you are referring to payments for sessions booked with Scheduling, these are paid through an entirely separate payment process. Squarespace doesn’t charge any additional fees when you take payments with Scheduling, regardless of the plan, but each payment processor has its own fees.
You can change your Squarespace website plan and cycle at any time. If you are upgrading your plan, you’ll be charged the prorated difference between the two plans based on the remaining time in your billing cycle. Your billing cycle and renewal date won't change.