SLA Breached for 3 months - No Result

I have written and called for an explanation ever since I was prevented from using my account in December without being told why. So Dec I have had no joy from this company and service thereof. I also wasn't given an invoice when I was entitled to a refund for the inconvenience caused. What is the SLA agreement time of ticket logged? I have been informed by accounts that they are looking into the issue, but no one has contacted me with any compelling justification, so I simply ask to have the service/line closed or cancelled so that I can move on to your competitor who will and might do a better job. I can't do it any longer, and enough is enough.