Can I turn off features I don't use?

No. Individual features can't be switched off or hidden in VirtualCallboard or StageStock. Every site on a product has the same features, apart from paid add-ons like TXT messaging, even if you never use some of them.

What each person sees is shaped by their role, so people only get the menus and buttons their role allows. A StageStock plan can also be turned off entirely if you only need VirtualCallboard: someone with the Account Billing permission can do that under Administration > Invoices/Payments > Change Subscription Package.