Data: Gone in 13 seconds

Last night I purchased 5Gig valid for 7 days to top up my work contract. I purchased under Made for you. As I was on my gmail, a message came through stating 50% of data uses. Some seconds later, 80% used. I turned off my data, then asked for a statement. To my surprise, I saw that 1 gig was used within 13 seconds of purchase, and another gig within 26 seconds. What happened to my data? Please return my data.