BILLING

I have advised Cell C Mon 2015/07/20 09:44 AM change Of Bank Details - ***, from the 01/08/2015 I have been billed against the old account and my bank chargers keep growing due to Cell C negligence within their Billing Department, why is instructions not followed through and why am I held accountable for an over-site , customer service is non existent at Cell C as one is passed on from one department to the next and nobody within such a Huge Telecommunications Company is willing to take responsibility and address the issue. Feedback at the third network email address is only responded to by Juanita Venter (Customer Service Manager) if it is a compliment , if it is a complaint it is not addressed , so my question is what happens to the Client in the meantime !