Billings complaint

Hi, i have been charged excess data usage by Vodacom for the past 4 months, despite controlling my usage via their \My Vodacom"App. Vodacom does not supply me with evidence as to which websites or downloads have i used or made. The itemized billing only states time and duration of usage as well as rand amount used. On 31 Dec 2015 i only turned wi fi on after midnight in order to use the \""Night Owl Bundle\"" i had available. However Vodacom has charged me 1GB excess of data at 22h30 on that day. The information is not correct as i was controlling my usage and had the wi fi off until midnight. I upgraded my contract to a 5G in Jan 2016 and upgraded my device. The new contract kicks in on 1 Feb however they have already charged me for the device on the Jan bill"