Data disappearing

I had used up my data bundles and had one day to wait for the new 2GB bundle to come available. In cases like that I will just use my SIM card from my cell phone. I know it can use more airtime than data time but I had done it many times before measuring and seeing it doesnt use very much more. I had data bundles remaining on my cellphone SIM card. The message said 500MB expiring in a day so I decided to use it. Just to check email. I checked how much airtime I had left. R185.19 plus 500 MB data. I sent one email and checked weather. The email was written offline first and just copied and pasted. The weather was just a click to a link. Maybe 2-3 minutes if even. After I checked my airtime again. R53.19. So tell me how can I use R132.00 for 2 minutes online. <br> <br>