Rain debiting additional unknown amounts

I have a month to month contract with Rain. I paid my premium on 30 April 2021. I was a few days late but I emailed them to check if there will be any other fees. I received an email reply that only R479.00 is needed. However on 1 May 2021 they deducted R47.90. Why is this so? I want my refund of R47.90 asap! That is not your money as my premium of R479.00 is paid in full. You do not have consent to take a further R47.90 from my account!