Wrong Bill on Roaming

In December 2014, I went Overseas and when I came back I received a bill of R79 000,00 for data roaming. My data and data roaming were switched off. I used Wifi at all times. I travelled Overseas every month and I know what to do in relation to data roaming to be switched off. I logged a request in January 2015 and the request was closed and no response at all. I went to Sandton Branch not another one and still there was no response. Now I have to log another request today and the data centre telling me that my two previous requests were still pending and I cant believe while this delay and is taking long. My phone line is blocked and I cant make any calls because of the data roaming that were never used but billed for. I am thinking of closing this account and go to another service provider, this is so ridiculous from Vodacom to billed me wrongly and it is unacceptable.