It's important to note that SMS usage alerts are closer to real however in some cases they can be delayed by up to 48 hours. In regards to the My Optus app, typically usage information is updated within 4 hours. I'd suggest checking your usage in the My Optus app to confirm when your usage was lasted updated. We don't charge you for data that wasn't used on the Optus Network.
@arenh - Thanks for getting in touch with us. We provide a number of self-service options which allows our customers to track and manage their usage - I can confirm that we only charge you for additional data that has been used on your service that falls outside of your plan inclusions. It's disappointing that you feel that way however we'd be more than happy to go through this with you. The break down of your data is provided directly on your My Optus app - if you require further assistance however please chat to us here → http://www.optus.com.au/shop/notices/service-chat/