"Suspend SIM" - means that you are suspending the SIM itself. When the SIM is suspended, the endpoint will be disconnected from the network and all teleservices (eg. SMS and Data) will be disabled. You also won't incur any SIM hosting fee in the next month when SIM is suspended. (SIM status will be changed to suspended).
SIM can be activated anytime.
"Disable" - means that you are disabling the endpoint, not the actual SIM. When the endpoint is disabled, all teleservices (SMS and data) will not work. The SIM can be removed from the device's endpoint and place to a new endpoint or device. Since the SIM remains active there will still be a charge for SIM hosting fee. (SIM remains activated but the endpoint is disabled).
An endpoint can be enabled anytime.
"Release SIM" - means that you are releasing the SIM from the endpoint. It is useful if you want to recycle your endpoint and put another sim on it. (SIM remains activated but no endpoint assigned).
You can always assign a different SIM to an existing endpoint.
"Reset Connectivity" - This action will trigger the endpoint to perform a refresh or reset of connection. It disables and enables the EP, suspends and activates the SIM, one after the other. New attach procedure will be performed and connectivity will be shortly interrupted. (SIM and endpoint status remains active).