Sell you a top up data deal- End up paying almost R2000 for a R200 deal

Earlier this year, i upgraded my tablet to a top up data contract with a wifi router. The deal was R200 pm with 5gig day time data and 5gig night time data.. eventually i started seeing that my invoice for that package is now R230 all of the sudden... Then they dont tell you that once your data is finished you will be paying for out of bundle rates. This means that in a weekends time, my bill went from R200 that it should have been to almost R2000. This is the second time this has happend to me with vodacom. They are the worst cellular network that there is, and i would like to cancell all 3 my contracts with them as they dont tell you the small print. Atleasr tell people that they should monitor their data so everyone dont end up spending their whole salaries on stupid data for 2 or 3 days.. i am sick of vodacom. I will never in my life use their services again!!