Over billing

I've logged several billing queries which are closed but the issue has never been resolved. I have to date not received a single telephone call to discuss the matter. Every agent promises to escalate and call me, but never do. Once I received a credit for a single month, which means they agreed that a mistake was made, but did half a job as they never removed the Service from the Billing, so I am still being charged every Month for a service that never asked for, used or ever received. I need connectivity for work, this is completely unacceptable. The level of unprofessionalism is astounding.