GETTING FED UP WITH VODACOM NOW

i never had problems with vodacom before but this is the 2nd time im having issues with them i have a contract with vodacom a smart tab 3g it was a open line contract and i had to wait 3 months to change it in that 3<br> months i never had data problems i got 500mb for free every month and only used that in Aug is phoned to migrate to top up and it was done i was told from the 1st my contract is top up now all of a sudden i migrated but now my bill is R2327.73 all used on data but before i never had that problem i have 3 contract with vodacom and every month my bill is R588.00 standard amount now that i have migrated vodacom is coming with a story that i owe them R2800.00 on data used but i switch my data off i hardly use my tablet. i hope that t his issue will be resolved because i refuse to pay R2800 for data i never used. i cant wait till my contracts are done i refuse to take anymore contracts with vodacom too much issues now