SIAM has the ability to terminate a SIM card. Terminating a SIM stops the SIM card from functioning and prevents further billing of the Service Charge (but will incur a cancellation cost if the SIM card is still in contract).
To suspend a SIM card (suspending a SIM stops the SIM card from authenticating on a network, however you will still be charged the Service Charge) see, How to suspend a SIM card or How to bulk suspend SIM cards.
This is found at SIMS > SIMs List > Action > :
If successful the SIM Network Settings will appear:
If successful the SIM change state form will appear:
If successful the following message will appear: