over charged again

You have over charged me again, after i took the time to go to your headoffice to try and sort this out. I need help from someone who wants to help and do their jobs please. Every month i am paying for a 500mb data bundle. In September i used 383mb yet you charged me R326 for this. I used less than the time500mb already paid for, please refund me. In October i used less453mb of data and i was charged R144 another refund needed. Can someone get hold of me yourAGAIN and let's hope this time is sorted out once and for all.