The Top Up History tab allows you to view the history of your top up payment, with the specific data and time, transaction code, response status, whether it was approved or failed, amount credited, and the invoice for the payment. Only a top-up with a response status of Success will be credited to your account.
To view top up history and invoice, hover over the Configuration icon from the Navigation bar and click Billing. Top Up History and Invoice is the fourth item in the menu bar.
Clicking Show Invoice will display a 'printable version' option for your invoice.