Bad service, Billing and account

I have been in contact with vodacom since last year about my modem contract account that ended last year august. Vodacom had debited my account even though I had paid for the last outstading amount that I owed. In the middle of this year I started receiving invoices that I owe vodacom for data on my modem that I've finished paying and not using I don't even know where the modem and sim card is. When I called to find out why am I getting statements and invoices I was told I upgraded in April of this year which is a lie. I was also told again in august when I called that they'll rectify the mistake and refund me my money end of September. This hasn't been done even today. I'm fed up with the service that I've been getting and the lies I've been told on several occasions by vodacom consultants. They leave me no choice by to sue them because they are *****ing my image and name.