No resolution

It is time for an upgrade on my mobile contract and I have been billed out of bundle rates with no notification whatsoever. When I contacted the call centre on numerous occasions I receive different feedback each time. When I ask to speak to a manager they are always unavailable or the agent refuses to get one to take the call. I got to the Cresta branch and I was told that they cannot remove one of the services on my existing contract before I can upgrade. They had to log a case. In the meantime I'm being billed extra. I find this totally unacceptable. Poor service all round and no follow through to date.