Vodacom insane monthly bill on DATA

I have 3 devices at Vodacom Main number listed in contact details Month end i received i bill of R 5306 On every notification on my data being depleted i uploaded more data 2 mins after the sms notification According to the operator R1800 has been charged on out of data rates... HOW IS THIS POSSIBLE?? And on my vodacom app my total monthly bill will reflect the same for 2 - 3 days and the it raises from 12 May R2034.91 to R2058.70 -15 May later on 15 may R2086.70.....Why? i have data and minutes.... Please i would like my money being paid back if you can proof to me why im charged so much... i couldn't even pay my rent this month because of this... :( Very Unhappy client...