multichoice is a ****

i have a contractual problem with them ,i have a contract with them that requires me to pay them 499 as it was stipulated on kthe telephone consultation with their sales lady .now the developed this money making scheme that if on my due date i failed to pay before the stop the subscription they start to calculate the prorate moey of which i dont undertands wher they agree with me ,and i only know that whatever that we agreed on must be on the contract and i never requeste that to be initiated on my contract with them and this was ongoing for the past 2years