Day light ******* at Telkom

Telkom did not pay all the money they took on my account while solving my case they are owing me an amount of R475.19 according to my calculations ,and also they took my instalment money before the contract date , from what I know I pay on the 20th of every month but they told they did acted the already on the 7th of November of which they claim is for November 20 .I have no problem with that but why rob me so much money ?