Outrages bill

I was on a my gig 5 contract from Vodacom. as soon as my data ran out I could not connect to internet. I changed to a my gig 2 contract in feb online as the 5 gig was getting too expensive. this month my bill is suddenly r4000 rand. I called to query why and was told its an open line. this was not told to me and due to previous contract being closed line I wasn't aware that this new contract works like this. who has R4000 lying around for a phone bill due to Vodacom outrages out of data rates. I need to get this reversed or arrangements made to fix this as I do not have this type of money for Vodacom. I will reverse this debit order as I was not informed of this being open line. Vodacom customer care send us to shop. shop told us to call accounts. accounts cut us off and cant help and told to go back to shop. what now?