My invoice is too high and not as per contract

I just spent 45 minutes on the phone, of which I probably waited for 40/35. When it looked like I was finally speaking to the right person (your 3rd consultant) my phone died and the consultant did not call me back on my cell phone as requested. I am not going to go through this process again, and since I cannot email you... this seems the way to go. As per the DO broadband package that I am on, I should be paying R356 per month, as per normal. Suddenly I receive an invoice with changes, which makes the total R375. You cannot just do that and I want it reversed please. Thank you.