Bad Service and Bullying

I have an Uncapped Lite 3g ****le now for 4 years. I understand that throttling happens after the 3GB usage is up. I receive an SMS on this every month and that my throttle speed is now 256 kbps. I am fine with that. Suddenly they throttle me to 64, after the SMS stated 256 (as per contract) . Now, I complained and was told I need to upgrade and that is it. I wonder how far the open-ended mobile contract issue in South Africa can be taken back with people that had to pay an additional month.... and in this case MTN has to abide and they refuse. Such bullies!!!!