Deducting airtime without consent

I bought a promotional, "R10 for 30 Minutes" deal and received a message to confirm that the R10 was deducted and that my available balance is now R19 and I have 30 Minutes that I can use between 6am and Midnight on 26 September. I made a few phone calls and probably used around 15 minutes of the available 30 minutes.

Without making any calls in between I attempted to make one today, only to find out that I have run out of airtime which led me to the conclusion that after deducting the R10, Vodacom never activated the 30-minute deal and charged me full price for the calls i made.

Dont trust Vodacom!