Interlace — BSNL Broadband Connection is not working

I got the BSNL broadband Connection One week back...But the Last 4 days the Connection is not working. I called many times Customer Care (1500) and they told me that to change the IP address and even it is not working. Only Internet Connection LED is not glowing. They asked me to go to the router page(http://192.168.1.1) and my user name get chnaged into "muliplay" ..I dont know how it was happened...After that I chnaged my correct user name and password. Even it is not working..

My Modem model is ZTE...