Just want to be assisted

I am a prepaid mtn customer. I have been for nearly 20 years. <br> <br> Yesterday (14 April 2015) was only the second time in the nearly 20 years that i experienced this problem which is this:<br> On Monday the 13th of April i bought an R180 recharge voucher. MTN awarded me with two R50 MTN - MTN vouchers. I made two calls that the morning that in total lasted less than 10 minutes. During the course of the day i i checked my balance and it was over R200 (including the rewards i'm assuming). Later that night i made another call that lasted less than 20 minutes. I checked my balance again and saw that i had R50, and after the call just over R26. <br> <br> I tried calling their prepaid number, 173 numerous times and was not able to speak to a consultant as it does not offer that option. I then googled their contact numbers and dialed 1761. Again, i was unsuccessful as they were closed. <br> Today, after holding for over 15 minutes i came through to consultant only to be informed that it's the contract customers helpline. She politely transferred me to the prepaid call centre and surprise surprise, it's the 173 line. <br> Please help! I use wifi at home and work. Where did my airtime disappear to?<br>