Bought R100.00 and the next morning theres nothing

Good day,<br> <br> I am a long standing client of MTN. i have been using MTN as my network provider and this thing that happened recently i dont understand and hope that MTN will be able to come up with solution. I have contacted their Call Centre and i was told that i logged in to Internet and it took R79.00. <br> <br> I bought Airtime on the 28 May 2015 and the next morning i was without that Airtime. I am so angry and furious with their call centre that is always saying services has been destructed! <br> <br> Please provide me with report of how did airtime just disappear like that without subscriptions