airtime disapearing

i loaded airtime to the amount of 40.00 after i loaded i checked balance and it said 39,80 which i ignored because i wanted to buy 39,00 data. I then try to buy data and it says i cant as my balance is 34,57 I call the call centre and betweend agens Brandon, (rude) Slindokuhle and (needs to fired or training ) Zandile Nomber and the supervisors who are Meshan Naidoo and Menzi Magubane or Ngubane no one could tell me where the airtime went. all they can tell me is that there was no usage. I was on the line for over 3 hours only to be promised a call back after 72 hours meanwhile i had to load more airtime to do what i needed to do. coz as per Zandile and her teammates im wasting their time calling for 5 rand. well excuse me its my hard earned 5bucks. worst service ever i expect my airtime back and my time and ernergy that i used on your *********** staff reimbursed.