Would a simple retry mechanism work here?
Send a request to conman, wait at most X seconds(with N retries) before marking conman entry as inactive and clean up inactive conmans in the background.
This way your client waits at most X seconds before being reassigned warm conman
There are even worse services where there is no UI to cancel subscriptions. You have to instead email customer support and spend another week explaining why their service sucks.
This way your client waits at most X seconds before being reassigned warm conman