Poor service as usual

I upgraded my Data contract last month due to being charged the normal rate. This month again (two months in a row) , I am debited with the incorrect amount - you get transferred to 10 different people who cannot help you...MTN is seriously frustrating. I upgraded to a same contract that I have always had for R89 yet I am debited with R143... then I am told that MTN forgot to apply the discounts. Seriously.....this is what you do ALL the time to