Mtn upgrade horror

If I could give this a half rating I most certainly would. I have been trying to upgrade for 2 months now with no success. When I initially wanted to cancel my contract someone from the retentions department advised me not to. And put me on a month to month contract advising that I could upgrade at anytime. To which I agreed. Now when I decide to upgrade I am told that they are getting a Siebel error due to my account not being carried over to the new system correctly. I have been to the store, I have called the call centre, but customer care is clueless and sends me on a wild goose chase. For the past month I have been trying their Facebook page but just like all other attempts this too is useless.