4 GB Data bundle depletion in 24 hours

I have a contract with Vodacom for a 3GB data bundles. The data bundles were loaded on the 02 June 07:26 and by 14:38 only 5MB was left. Which is highly impossible because i only use it for hotspot for whatsup. The whatsup usage was 480MB. when i looked at the phone data usage it indicates that Tethering and portable hotspot usage is 3.97GB but when i call Vodacom they claim its internet usage. I do not use the phone during the for internet as i am at work. <br> <br> Something doesn't add up. I have been using the hotspot for the past 3 months and i never depleted the data bundles. From may 2015, i started experiencing this and it gets depleted on the 3rd day of the month. <br> <br> Please assist.