Error on billing

I received a bill from Vodacom Data contract which is over R2000, apparently because of additional data usage. I have a block on my account for going over my data limit, and also normally receive a SMS notification when my data is finished. How on earth can I suddenly receive such a bill if I received NO sms to notify me my data is finished, and my account was never blocked. I logged this with Vodacom over a week ago, and was promised feedback within 48 hours, still waiting. Now, when trying to log into my account, I get a message that my account is in arrears, but it was paid at the end of last month, and is paid by debit order ever month, how on earth can it be in arrears. The number provided is my cell number, this query is on my data line.