Overcharge -Insurance

My mother is an elderly person. I have noticed that her DSTV account is very high. I was told that she is paying insurance for 3 decoders. She is billed for one subscription. 18 January 2019 I requested the insurance department to cancel the insurance and also asked for a credit for the 2 units that she has replaced over the years. The next day I was phoned by an agent to inform me that he will cancel the insurance and he also mentioned that he can see that my mother requested them to cancel the other insurance when she took out the new insurance. He also said that a credit will be passed for the incorrect billing. I requested a new statement showing the credit and twice other agents informed me that no credit will be passed as they cannot see the request to cancel the older units. I request DSTV to pass the credit as she is an old lady living of a small pension.