If you have run out of credits early in the month, you can renew or change your subscription early and receive the next month's 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.
How to change/renew your subscription
To renew or change your subscription click the Settings icon on the left hand navigation bar.
Under the Subscription and Billing tab, click Change Subscription.
You can then select the new level of subscription required. Under Renewal Date, if you are looking to change your 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 the current renewal date.