delete https://rtm.imiconnect.io/rtmsAPI/api/v1/apps/$(appid)/topics/$(topicid)/users?users="1234","5678"
This API is used to unsubscribe the user from a topic.
Know Your Endpoint
Based on the domain you use to log in to imiconnect, the endpoint for your API varies. See the endpoint section to understand which endpoint to use for your domain.