Data disappears

I have a data contract with vodacom. I checked my available data on 22/12/2015. There was roughly. 300mb remaining. In the morning on the 23rd there was 0mb. I checked my phone's data logger to try determine how this was possible. After some deliberation the only conclusion I could come to was that vodacom was being very devious in the way they conduct the usage of data, I loadwd a 30 day bundle in Nov wich expired on 22/12/2015. On 1/12/2015 my contract 1GB data was loaded.<br> Now comes the devious ********** part - obviously the contract data was used first and the bundle wich activation predates the monthly data, sat unused until expiry.<br> I suspect that this has happened in previous months but went unnoticed because I did not check my available data regularly. <br> <br> THIS IS BLATANT DAILIGHT *******.<br> <br> I have a contract with Cell C and they don't do this.<br> <br> I will be stopping this vodacom contract ASAP.