There are 2 options available:
You send GMS the Service ID deactivation request. Such a request should be sent before the billing date. This way, you avoid the MMC payment for the given ID.
Example: You would like to have an ID deactivated starting July. Therefore, the request should be sent no later than June 29. If the request is sent on July 1 or later, the ID will be deactivated only next month – in August. In such a case, the MMC fee for July will be applied.
You leave the ID active and do not send the request at all. In this case, you will pay the MMC for this ID.
Please note: Viber allows for up to 3 ID deactivations per year. After 4th deactivation the ID automatically becomes inactive and can`t be activated till the end of the current year.