Unknown billing and subscription

On 13 January I had R12 sent to my cellphone number *** by a friend and without warning or usage of my mobile that very day R7 was deducted from my account for a supposed subscription I did not even apply to. This is not my 1st incident with Vodacom regarding these unknown billing subscriptions and airtime deduction on my account with the last incident happening a few months back in 2015 between the month of September and October if I recall correctly. Now as a customer I understand mistakes happen and the first incident I was willing to let go but twice cannot be a coincidence. I kindly asked Vodacom to refund me my airtime and they refused, this is unacceptable. As I am a small fish in the ocean I ask you guys to please help rectify this cause it has happened to me again and I can only imagine how many more other customers and Vodacom users have incurred the same issue. I am a very calm person but this day light ******* and theft I will not stand for. I want my ****** airtime back!