R700 airtime gone in 3 days

I have no idea what is going on but I lost R700 worth on airtime in the last 3 days. My data usage on my phone was 500mb. I didnt get any notification that my current data bundle is finished. How is it posible that I loose R700 airtime in 3 days. I barely use my R500 airtime in a month and all of a sudden I \use"more than R700. What is going on with the Vodacom network as of late? """