Fed Up

I have a Nedbank account. A few years ago I cancelled my Greenbacks which was done with quite a hassel as I had to get a new card etc. Then about a year later they just started charging me for greenback without my knowledge or consent. I had to phone again and once again got it cancelled after speaking to a manager and got my refund. Then once again on the 3/12/2018 the start taking Green Backs amount off my account which is only R20.18 per month but over 6 months it adds up. I have not given them consent to take this out my account. I dont know what gives them a right to just do what ever they please. So once again I am on the phone complaining. I have a complaint number ***3. after the second call with the same reference no. they stop the debit order and refund me for one month greenback. so on the 9/5/2019 they Refund me R 20.18. But what about my refund from 3/12/2018 - 2/4/2019. No refund for this and it was all your fault. Nedbank still owes me R100.90.