How to disable appointments entirely?

Summary:

We are using NGS and have disabled all the Smart Actions for Appointment creation because our client does not want to use the Appointment activity type, however the option to create one is still showing in the action bar as an option on the Activities landing page. Is there any way to disable this option entirely?

Content (please ensure you mask any confidential information):

All I can find in help documents are options to disable or hide the buttons on various page layouts which does not apply to NGS. I am assuming this is somewhere in setup and maintenance, but am unable to locate where.