If you wish to deactivate AIRV for all your users, you may navigate to the AI Recipient Validation >> Configuration page in Control panel, then go to the Add-in tab and click the "Remove add-in for all users" button (as shown below).

WARNING
These changes will take time (days and possibly even weeks) to propagate completely on M365, which means that this is not a quick solution for any issues you may be experiencing with AIRV.

If you are looking to remove the add-in instantly, then this must be done at the client level as described here. 

If you wish to unsubscribe and deactivate the billing of the AIRV service, then please contact our technical support team who can process the request. After this is processed you will no longer be billed for AIRV for that tenant as of the next billing cycle.