Going in circles with never getting the job done

It has been weeks trying to upgrade my 1 of 4 contracts with MTN. I have tried via my local store and call centre and even email. The latest responce that is " the store should submit a dispute to the credit department" after I wrote a email telling them how frustrated I am that nobody is assisting me regarding my credit limit increase. No effort in trying to say they will sort it out. Just that I have to go to the store again and do the same thing again for them to email again. All this has been done!!!!! My last email today even had the full details that my first call was on 21 Jan to try upgrade. I have never struggeled this much to get approved in 10/11 years being a customer. Why now???