Disappearing airtime...HORRIBLE service

Everytime for the past year that I've loaded airtime, it disappears for no reason! And everytime I contact the call centre, they can't see what happened because their system has not updated. I have loast over R1000 airtime over the past year because it just disappears...I have been referred to managers on countless occasions, but there has never been an explanation for the loss of my airtime. Today I loaded R30 airtime and purchased a R3 data bundle, now I only have R15 left....MTN has never responded to any of my emails and I just want my airtime back! Their service is HORRIBLE and the consultants are quite rude. This isn't the first time this happened and I see I'm not the only person this is happening to, I wonder if MTN will even respond to this!