Why can't I get my own details?

I have been trying for the last week to get MTN to do a change of address for me. This is the 4th time over a period of time that I've attempted to bring my details up to date. For a company who are so strict on holding clients details, why can't they do this? It will be 7 days tomorrow since I went into store in Stellenbosch and the kind consultant helped me. Now we can't get a response? Secondly, MTN are telling me that I am due for an upgrade, as my contract expires in November, however, there is no way they can tell me on the telephone, via customer service (808 - Customer service, that's a joke in itself) what it will cost if I upgrade to a certain handset. Telkom have a much better deal on the handset I want, so yesterday I called 808, after hanging on for 36 minutes to speak to a consultant, they couldn't tell me how much it will cost to end my contract prematurely. Only the retention department can give those details,but they don't accept calls from the public!! I have tried but cannot register for self service and can't get the correct figure sent through. I find it so frustrating that even after talking to the consultant for almost 20 minutes i got nowhere.