Rain: ******** access into my account

I have never been so frustrated in my life. An amount of R625 was wrongfully deducted from my account by rain mobile, when I call to lodge a complaint, the consultant simply hangs up, I sent an email with proof of the amount that was deducted, but there has been no response from them since then. My main concern is, how they were able to deduct without a debi check mandate and how they were just able to gain access to my account just like that. I really need that money back in my account asap, and hoping that this review will get me the help that I need.