Airtel Broadband Services — Not Getting the Appropriate Speed

Sir/Madam,
I am using a Broadband connection of 64kbps, plan DSL Home 399 Package from about 10mths. when it is installed i get a speed of over 50kbps but now i am even not getting the speed of 20kbps.due to which disconnection happens many times/connection error, etc
My broadband service number is[protected]_mp and the billing address is
S P K LAZARUS
B/43, Kehkashan Apartment,
Kohefiza, Bhopal- BPL-05
Please help me. so that i get the appropriate speed to be connected.