Vodacom data billing is a big cheat

I have issues with the following, firstly is the billing method. Vodacom is charging me for data that I consumed between midnight and 5AM. I didn't expect to be charged as I have night owl data bundles. I started the download sessions at 0:00 as per itemised billing report. The argument Vodacom is giving is that they charge according to the time the session commenced which should have been 0:01 for night owl. I find it strange and unfair for Vodacom to charge per session. I expect Vodacom to charge me for the data I consumed before 0:00:00 and 0:00:59 and the rest should be on Night Owl bundle. The number in question is ***