Bad service

Good evening, I have a problem with Vodacom regarding their bad service. I have just upgraded my contract on the 11th November where I was offered 50GB all which I received on the 1st December, I only used my data on whatsapp on the 1st December but to my surprise on the 2nd at about 03:00 am my balance was 41.24 GB which is impossible for me to use 8.76 GB in few minutes on that day. I have send an email to them and copied CEO but to date no one revert back to me . The CEO read all 4 of my emails and ignored me I have promised not to be their customer again but I seem not to leave them , I have requested them to send me breakdown of my used data for that day but still no response, please help.

Unhappy customer