Airtime gone the call centre not working

On sunday evening I topped up my mobile number with R30 airtime and i purchased a data bundle for R15,00 after topping up and I was supposed to be left with R15,00 airtime however mobile phone had 0.00 balance so I wondered where the money could have gone to so i called the call centre for them to check they keep me on hold and the line got cut off and one of the agents picked up the line and didnt say anything I could hear sounds in the background of agents chit chatting. So yesterday the 25th of November i decided to call them so that I can get clarification where my airtime went to, an agent by the name of Neliswa picked up the line and kept me on hold till the line dropped or she dropped it I dont know.I used a USSD string to check if i have any subscription and the feedback i got from there this morning is that I dont have any , So now the only thing that makes sense to me with regards to my airtime is that MTN stole my money , i dont have proof for the allegation but they have to show me where my R15 went to.I Need my airtime back and this is not the first time im tired of supporting ******* soon im going to port out if you dont clean up your act and reimburse me my money.