Do you have extra credits in your account? Here's how you can apply credit to pay your invoice.
Log in to your client area using your username and password.
On the top right corner, click 'Notifications' to check your credit balance.
Under Billing, select 'My Invoices'.
Under Status, find your unpaid invoice(s) accented in red. Now, click 'Unpaid'
Scroll down and click on 'Apply Credit' at blue box for instant payment.
After payment has been made by using credit balance, you will receive 'Invoice Payment Confirmation' email.