Bonus airtime

I had an airtime balance of R32.and a bonus airtime of R100. I made calls using my bonus airtime , after my last call at 22h54 I had a bonus airtime of R3.98, to my surprise my airtime balance reduced to R18. Of which I dnt understand as I was always checking my balances before attempting to make a call. I then called the customer service no the same day at 22h58 but their number didn't give me an option to speak to the consultant. I called this morning speak to Adelaide Shezi and she said that she won't be able to log a case to technical department as the bonus airtime forfeited and she then referred me to go to vodacom shop. This is really nonsense, if vodacom shops can be able to retrieve all the calls and balances on my sim , really somebody from customer services can also be able to do that. I dnt want to hear any stories but I want my airtime to be reversed back to my account.