You have the option to buy 1 GB for extra surfing. You can easily do this by going to Settings> Mobile data, then clicking on Buy extra data. If this option is not available to you, contact your administrator who can buy data for you or add the option to buy.
Telavox alerts you via SMS when your account reaches 80% of its data packet and limits the speed at 100%. In cases of significant consumption over the surf quota, data is blocked and you are notified via SMS. If you wish to upgrade your surf package you can contact your administrator at the company so they can increase it.