Missing Minutes / Data

I have a vodacom contract which i use as a data line in a device that cannot make voice calls, however it seems that from the 1st of Sept to the 2nd i now only have 120 of 150 minutes left, how is this possible?<br> <br> Also i have a R4,500 data bill, which does not make sense as i have been using my mifi sparingly. Also my data allocation from the 1st of Sept to the 2nd has been used, even though my mifi device has not been used at all.<br> <br> Please advise as this is reason enough for me to settle and cancel all my vodacom contracts.