Airtel - Broadband — due to change in a speed

Address:

Tiruchirappalli, Tamil Nadu

Sir,
I am A.mohammed Affrin my airtel land_line number is[protected] am using the Airtel Broadband for the past one year in the plan of
Rs 770(699+tax) in this plan till last month[protected] i was able to download at the speed of 512kbps for unlimited (am sure i have downloaded more than 6GB in one month)the speed doesn't change even when i download it more than 50GB , but now its downloading only at the speed of 256kbps and when i asked for explanation they are saying that there is no such a plan like that and they are saying when you download more than 6GB your Speed will be changed to 256kbps from 512kbps and am sure about this(last month i downloaded more than 6GB at the speed of 512kbps) sir it was not happened in the past......... please reply me and kindly do needful sir.................