Missing airtime and DATA

On the 17 of January 2016 I had R27 airtime and I purchased 100MB of DATA using R12 of the airtime I had left me with R14 airtime left my phone without attending it for 30 minutes and when I came back my airtime finished and I had 7MB left, I call customer service and explained the story and the customer care consultant told me that is because I had multiple sessions on my internet usage. I explained to her that I also have been using this for a while it's the 1sd time I hear of multiple sessions and airtime and data been used at the same time, to my understanding it's not fair to buy data and airtime and when using the internet both data and airtime is used.<br> <br> I called MTN at around 12H00 on the 17 January 2016 and explained it but they told me it's my fault. <br> <br> I would greatly appreciate if MTN resolves this as it wouldn't be fair if I move to a different service provider simply because of a minor error<br> <br> Regards,<br> Robert Mangwane