If you have run out of credits early in the month you can renew or change your subscription early and receive the months credits straight away. Your monthly renewal then starts again from that date.
For example, if your subscription date is on the 1st of the month and the credits run out on the 20th, you can renew or change your subscription on the 20th and the monthly billing then occurs on the 20th of the month going forward.
To renew or change your subscription click on the user drop down top right and select Account Settings:
Under the Subscription and Billing tab, click on 'Change Subscription'
You can then select the level of subscription required and click Change. If you are looking to change subscription and have the credits added straight away, you will want to select the renew now option. If you are happy to wait until your usual renewal date for the subscription to change over, you can select current renewal date.
*** Note - Access to the subscription is only available to the billing account holder. Invited users do not have access to the subscriptions.