Charging me Incorrectly

Don't know where to start - it all began in January. I called in to upgrade my 250MB to a larger one, a 3GB one. I was told I needed to purchase a 500MB once off to get me through the rest of the month to which I agreed, and my 3GB would be active from beginning of February onwards. I assumed it was all arranged and left it at that. 3 months later I noticed on my billing, that my 250MB wasn't upgraded, but cancelled and I have now been billed almost R3000 more than I should have been (for Feb, March and April) because all my data usage has now been out of bundle usage. I have called in about 5 times so far complaining. Each time I call I get told they will investigate and get back to me. Its bee a month already and no answer / feedback. I call again and its the same story. They will investigate and get back to me. Plus on top of it now they have finally added the 3GB - but they did it twice in 1 month so I am getting double billed for it??. What is wrong with their systems that everything is so messed up??<br> I called early in April, about the 10th, then again around the 20th, then again end of April.