No response to billing queries!

I tried to upgrade my contract 3 months ago, what should be a simple task resulted in me getting a huge bill as i was upgraded onto an incorrect package (despite the cap on my account). This took 2 months to 'resolve' during which i was disconnected on numerous occasions each time have to spend up to 30 mins on the phone with the call center and explain the WHOLE story over and over. When i finally (after 2 months of trying) was contacted by the accounts department and they agreed to credit the amounts and just charge me according to the correct package i immediately paid the agreed amount. This was never credited to my account nor does the payment reflect on my statement. i then received a 3rd bogus bill which i once again queried and since last week have received 3 reference numbers and still no feedback! I can not believe that such a simple task can be so difficult and now think i am on the incorrect network. My phone remains cut off as i have not paid the incorrect amount! I have called, emailed and done web inquiries and still get no feedback! Very disappointed