data usage

On the 8th of August, I phoned the call centre and queried my bill for the month of July. I was informed that my bill was high due to my data usage. I recently purchased a wireless device with 2MB and was using this device to connect. When I spoke to the consultant, I advised her that I am receiving sms's stating that I am being charged R2.00 per MB where as my contract stipulates R1.00. She opened a query, I received notifications stating that someone will contact me within 48 hours but no call received. This is not the first time I am having issues with my data usage. You guys promise to call back but never do. Did any investigation occur, I don't think so. My bill came to over R2000.00 and since June I have been connecting to the wireless device which restricts me from going over 2MB. I don't understand why I was charged, secondly what was I charged for the data usage and thirdly, why was I charged if I was connected to the wireless device.