Users might find that the service channel check box in the agent workspace inbox is read-only.
Users will not be able to uncheck the channel.
This is an expected platform behavior if you have only one service channel.
The channel check box can only be edited if there is more than one active service channel in the available presence state selected bucket.
If you have only one active service channel added to the selected bucket in the presence state, then you can simply set yourself to Away of Offline if you are not accepting work items.
When you have multiple active service channels, you get the option to toggle between then and set then active/inactive as per the requirement.