Ridiculous Data Charges

I just received a 'friendly' phonecall to inform me that there are cheaper data bundles available than the R2000 data I have been using.<br> <br> I was shocked!<br> <br> My telephone bill has almost never been over R500 and now (since my contract has come to an end and 'rolled over') I have a data charge of R2000 on my account.<br> <br> I will absolutely not pay for this.<br> <br> Every time my data bundles run out I immediately purchase another one with the vodacom app on my phone - so to my knowledge I never use out of bundle data.<br> <br> Please could you urgently get back to me with the details on how to go about reversing this ludicrous charge.