Unsatisfactory service

I have been struggling with my account since end of April where they charged me R6500 for a device charge, they keep telling me its been esculated. A very nice lady i spoke to said it was a glitch in their system as they were changing systems. I kept calling to have my account resolved and they kept saying its been esculated. Today is the 30th of June and i have still had no luck, they call me and when i retell my story for the 100th time all they say is they will esculate it. I will not pay this amount, and they want to block my account. I have been with MTN for more than 10 years and always something