Contract Billing and Incompetence

The past 5 months have been a nightmare with Vodacom. Last week I posted a complaint about me paying for contract cancellation in April which they have failed to do so toll this day and i have been billed since then, a gentleman called me following my complaint and said he will contact me, a week later he still hasn't contacted me. This evening I received an email from Vodacom with my monthly statement and the statement says I owe Vodacom over R10 000... HOOOOWWWWW does that happen when i have paid for the lines to be on prepaid since April, how Vodacom, i have just had about enough of this nonsesnse, can someone competent and more senior give me a call regarding this.