Missing airtime issue still not resolved after promise to credit me

I'm Sibusiso Kevin Mohlaba , *** . 25/03/2016 I loaded R10 airtime and bought a R10 voice SMS data bundle , I loaded R30 later on and bought 2 R10 1gig midnight bundles , my balance was R10 , someone sent me R 10 airtime and my balance was R20 after an hour I checked my airtime and found R5 exactly , called customer care they told me they couldn't see where the R15 ended even when I called later , they told me they would credit me after 2 minutes , I've been waiting since , I called again and was told I sent a R15 SMS ,how is that even possible there is no such SMS on my phone , I had my phone the entire time Refiloe just wanted to close the case by lying <br> <br> I've been with mtn through thick and thin but this really disappointed me please help