Changing rules without customers\\\' knowledge

Mobile phone operators are often changing rules without informing their customers of it. I am a GrameenPhone subscriber and I use this network to browse the Internet on my Smartphone. My mobile phone number is 01716013979.  A few days back when I tried to surf the Internet, I was unable to do so and soon I received an SMS informing me that to avoid the bill shock, my date service was blocked despite having 300 MB data and a fortnight before the date expires. When I called the customer service unit, they told me that as I was using a 250 MB package I could not use more than 450 MD data even if I had been carrying more previous data from my earlier packages. The authority has taken this new decision without informing their customers of it.
I was really surprised to learn about the new condition and was very upset. How can the GrameenPhone change rules without informing their customers of it. They could have informed their subscribers through SMS about the new rules. But they did not think it was important. For, most of the time the customers remain silent and they do not find anyone to listen to their grievances. So, it encourages big companies to neglect their customers.
I urge the Posts and Telecommunication Ministry to launch a help line so that the customers can lodge their complaints against any mobile phone operator exploiting the helpless subscribers.

Mohammad Sohel Hara
Banasree, Dhaka