DSTV unauthorised bank deduction

I Had price lock plan with DSTV which expired, and I received confirmation lesser amount would be deducted from my bank, however DSTV proceeded on 1 March to deduct the same R529 amount again. I send them a email to inquire and instead of reading my complete email, they just respond and close the call with incorrect information and they do not answer my concern or questions, and say nothing about how they are refunding the wrongfully deducted amount