Airtime and data I buy disappear

Hi, <br> <br> On these dates: 9th, 10th and 11th of August 2015 I have been buying mtn airtime vouchers and either convert it to data bundles or keep it as an airtime. I am not sure how they are charging me but R15 airtime or 50MB data bundles don't last for an hour, in fact an hour is long it doesn't last 30 minutes. I called mtn 173 help line but I couldn't get assisted. I wanted to find out if I subscribed for something i didn't know of which is highly impossible because I did nothing new on this phone ever. When I called mtn 173 service line a consultant by the name of Dumela who was rude and wasn't really willing to assist, told me she sees nothing wrong with how they charged/ took my airtime and data. I thought this was over until I loaded another mtn voucher of R10 today at around 13:30 which I bought a weekly data bundle and didn't even touch my phone after buying the data bundles but now all the data bundles are gone. I don't understand how is that possible. Your call center couldn't help me, I hope you can because I can't afford a network charging me R10 for 10 minutes even if i use it or not. <br> <br> I now await your resolution<br>