Paying For Things I Never Asked For

I upgraded my phone and changed contract package because my old contract package no longer existed. This was in July. There was some sort of glitch on the system and for July I paid for both the old and the new package. After this I was finally migrated to the new package, but there remained bundles that were on the old package that should have been cancelled but I am paying for them still!!! It has now been 3 months, I have called over and over and people keep saying they can't do anything about it because it is not a closed invoice and that when the money goes off I can call and they will refund on the next bill. I do this EVERY MONTH! Nobody is willing to fix the issue but MTN is more than happy to take my money for things I don't use or want!!! PLEASE SOMEBODY CORRECT THE ISSUE before I am forced to go to the police!