Airtime disappeared

I had R47 left of the R60 I had recharged, I also had R11 of the mtn to mtn airtime that expires at midnight. I was on a 5 minute call to another mtn number, there is no way in hell a 5min call can take R57 odd leaving me with 0.89. When I call 173 I am on hold for a good 20mins. I am unhappy with this billing error, and need to be reimbursed. You cannot say it's data as I still had 55mb and am now left with 23mb. I've heard clients complain of this before but this is absurd.