Air debited on my cell number

On the 1st of January received my monthly airtime of R150 as per contract and I never made a call. I was so surprise to find out all my airtime is gone on the 2nd of January 2016, I called the call centre on the 02.01.2016 and spoke to the lady called violet , she told me that I have subscribed to some company and they are debiting R7 per and I couldn't understand because I have been recharging my phone with prepaid and it was never debited, she couldn't give me the reason why and all she said was I will cancel it.she told me she cannot be on the phone for long therefore I need to cut it short and accept that my air time is gone. i requested to speak to her superior by the name of selwyn who also said they are receiving a lot of calls and will assigned my query to technician and will come back to me in 24 hours. I asked for a call reference and it was given to me as *** and until now I haven't received any call or feedback from Vodacom. I've been a Vodacom customer for 15 years and never missed and debit order.