Yes you can add funds to your account. The first stage would be to generate an invoice.

    Click here to login to your clientarea
    Once logged in, click on Billings->Add Funds
    On the Add Funds page, enter the amount of money you would like to add as credit to your account and choose the payment method.
    Click the Add Funds button. Your invoice would be generated and a mail would be sent to your mailbox
    To view your invoice, click on Billings->My Invoices

Feel free to send us a mail if you have any issue.