Charged for insurance on two decoders

I would like to know why am I charged for insurance on two decoders. I am only using one decoder with serial number V ********** 42 and I took out insurance on that one. I cancelled the insurance on the other decoder last year and I got confirmation of that but since this month (January 2018) I was charged an additional R20 for insurance for the other decoder which I don't use and which I cancelled. I am supposed to be paying R809 and NOT R829. I paid R829 already for this month and I am charged this amount again for next month.

I would please like my R20 to be refunded as I cancelled the insurance on the old decoder as I am no longer using it.

P.S. The call centre agent, Palesa from Port Elizabeth was unhelpful and rude!