Reliance Netconnect — Repeatedly over billed the monthly rent

I have purchased Reliance Data Card and started using from Mar 2009. Over a Period of time due to improper services I stopped using the services and then a Senior Executive Mr Saurabh Gupta in Reliance Mobile asked me to restore the services by giving the assurance of best of the services. I agreed and I choosen a 300 Rs Monthly Rent Plan by confirming it on the application undersigned by me.

Unfortunately, the same month in Feb 2009, the bill amount was 702 Rs in which they have charged a monthly rent of 650 alongwith a late fee of rs 50. I tried to solve this issue with him and finally after 14 days the additional amount was waved out and I paid Rs 370.00 all together.

Now, again this month (Mar 2009) the bill amount is Rs 640.00 which is forcing me to loose my temper.
These (bast's) people have no value of their promises what they make at the time of sale.

What to do to stop all this nonsense ?????