My airtime just vanished and its your fault

Yesterday night I bought R100 worth of airtime that I loaded onto my phone. I also had 65MB of daily data. Before I went to bed I called my gf on Viber, using video calling for about 8 minutes, in the middle of this call I checked my balance as I was worried the video calling would be costly and I might need to buy more data, bt my data Balance was still 53MB and my airtime was still R100. After my call with my gf, I watched a video online that was about 8 minutes long and I watched about half of that video. The next time I check my balance was just before I went to bed, and my balance was now 7MB and to my shock R0.00 on my airtime!! ***!! How the hell did my airtime get spent. ???? Even if I used during the video, why did your systems bypass the data and use my airtime and not give me a warning that my data is finished??!! This is total bs and I want this to be sorted out and my airtime reversed back to me!! Cos even if the video used my airtime to play, there is no way it could have been 100 MB for a 8 minute video!! I'm so ****ed off I want to port out of vodacom, I'd rather go to MTN than this BS!!