Penalized for having paid my subscription earlier

Multichoice just can't disappoint especially lately. This time they overcharged me on my subscription. I took it light as an error that could easily be fixed. To my shock, I was told it's my fault for having paid my subscription three days earlier. I was then told that going forward I must pay my subscription on my last payment date and not earlier. I listened to that call recording over and over again and still can't believe it!