Charged a full month for one day's worth of contract, missing airtime

I just upgraded to the Uchoose 375 plan. It was supposed to switch over at midnight on 31 July. But instead it somehow started on the 30 th of July and Vodacom has charged me for the full month, even though it was only one day. I am also supposed to have R375 of airtime - I bought data for R149, voice minutes for R59 and R10 SMSes, but I only have R39 left for the month?? How does that work, where is the rest of my airtime?