Migration application problems

On 7 June 2014 I signed a migration application. I wanted to migrate from Mtn 1500 to Mtn sky.Charl at the branch assured me that it would be activated the following month. It did not happen, every month I would go there and complain and every time I was assured by Charl that it's sorted out.Problem is that Mtn Skye is a fixed package and with Mtn 1500 my monthly bills were much higher, some months even a R1000+ more than the Skye package.This continued until January 2015 when they eventually changed me to Mtn Skye after I signed for a new upgrade phone.Mtn still owes me the credit for all the months that I was charged more than what the Skye package cost. Once again, I am getting no service from them with regards to this issue, there is always a story and then nothing happens, I am so tired of begging this branch for service, I have been an Mtn client more than 20 years, and this is the type of service I get.