Data Usage bill

Last month October 2015, on the 14th of the month, my line was soft locked due to my limit being reached. I was told that my data usage for that specific day was R 1621.82, still do not understand how this was possible. Anyways Vodacom called me back soon after and offered me a goodwill gesture and wrote of most of this amount. This month November 2015, on the 14th of the month yet again, my line was soft locked due to my limit being reached. I am still waiting for Vodacom to get back to me, as i do not understand how is this possible. My cellular data is switched off most of the time, and i use wifi. If my line was locked on 14/11/2015, how am i charged on the 15/11/2015 for data usage? Last month my data usage was 2394.364MB at a cost of R 1621.82. This month so far my data usage is 2462.321, more than last month at a lower cost of R 1424.30???, this is according to your itemised billing.<br> I asked for an investigation to be done when i called in on 15/11/2015 - still waiting.