Problem Definition

There is an experimental end point to remove customers from a service desk using the REST API for the cloud version of Jira Service Management:
https://developer.atlassian.com/cloud/jira/service-desk/rest/api-group-servicedesk/#api-rest-servicedeskapi-servicedesk-servicedeskid-customer-delete

This feature does not exist for the server or data center version of Jira Service Management.
Here you can only add customers to a service desk using the REST API.
https://docs.atlassian.com/jira-servicedesk/REST/4.15.0/#servicedeskapi/servicedesk/{serviceDeskId}/customer

You can only remove customers from service desks manually via the admin UI.

Suggested Solution

Introduce a REST end point to remove customers from service desks using the REST API for the server and data center version of Jira Service Management similar to the end point present for the cloud version.