The way your plan works is: it provides a ceiling – a maximum number – of active users in a period. It is a fixed amount each month (or year). There is no concept of partial billing in our pricing plans. Therefore, if you signed up for a 500 user monthly plan, the amount charged each month is the same. Whether you had zero, 10 or 500 users does not matter. However, if you have 506 users in a month, for that month alone, you will get an additional invoice for the 6 extra users at the rate specified in your plan for additional users.