Missing Airtime to Receive WOW bonus

I recently decided to start utilizing the MTN WOW bonus promo that they have running, it stated that I need to use R7.00 on data, call or SMS's upon purchasing R7.00 airtime from the internet banking to redeem, this is when I noticed that I had missing airtime to receive the WoW bonus. I called the customer service and was topped up with a R1.00 in order to redeem the bonus, on the 02/09/2015 again I bought the same value of airtime and was short 94c, i was advised by the Call Center that this was for content/subscription services, which i dispute as I'm not subscribed to any. on the 08/09/2015 again the same occurred however this to only shorted a 6c, and this time was told there is a delay with there system updating transactions and would receive it after they refresh my account and i restart my device, which never happened i had to buy airtime in order to receive the not so wow bonus. Today i am short of a 2c in order to redeem, Please MTN explain to me what are these deductions on my account as this is way to little for any premium rated SMS or subscription service, which I dont have.