Missing airtime

10 February 2016 I had airtime of more than R11 and data bundles of more than 10MB but somehow my airtime was deducted for as per MTN DURBAN my internet usage, the agent that i spoke to Nolwazi Myeza even told me that no, that normally happens its just that mybe I am not aware. I am using a Nokia Asha and it uses mobile data to access the internet hence I purchase data bundles to access the internet and my airtime is for making phone calls. How is it that I always use data for all my browsing and are able to browse all these websites without airtime but now suddenly I have airtime and it is taken while I have data bundles? Why was I charged R10.66 when I had 10MB of data? I just want my airtime back. This is bad service. Even spoke to a team leader from the Durban, she's an indian woman, only got her surname Adam, i think she said her name is nakita Adam I am not sure but she promised to reverse the airtime back and it will be done within 2/24 hours and I am still waiting. Please resolve this.