Log into the Management Console of your ZelloWork network. Select "Billing".
Subscription and payment details will be displayed. You can increase or decrease users in the subscription section.
Select "Modify subscription" to change users or gateways. and you can fill in a different number of users to increase or decrease. You can then "Continue" to payment options.
If you have increased number of users, your payment will be made after entering payment information.
If you decreased the number of users, you will see a credit balance.