Your unbilled usage is under the ‘Payment menu’ item and the billing tab. The unbilled usage is available for your mobile numbers and fixed line numbers and represents the usage which was not yet reflected on your bill.
If you do not see your unbilled usage, it may be that it is currently disabled. To enable your unbilled usage and billed itemisation, go to the ‘Settings’ page and ‘Manage billings accounts’ section. Choose the GO account for which you would like to enable unbilled usage and itemization. At the end of the page, you will be able to change the settings and press ‘Confirm changes’.