You will start your subscription with a Free plan. The Free plan can be changed whenever you want, and it will be changed instantly. All plans last 1 calendar month, except for the Free plan; it doesn't have an expiration date. For a paid plan, you can choose a plan one month in advance. Any plan can be ordered for an Account, except the one that is already in effect. All users can view plans available, but only the Account administrator is allowed to order them. The message allowance depends on the plan and can vary greatly between plans.