Has my broadband been hacked?

I am using Airtel broadband connnection with Beetel wireless router.
first i notice some DNS problems as i couldnt logging to facebook and google for sometime, i then logged in to the router admin via 192.168.1.1 then changed my wirelss password even though i checked and no other person was logged in, after that the problem stopped and i was happy again.
Just yesterday i just wanded to loggin in to 192.168.1.1 and i noticed my username and password not working again, now i cant log in again.
any solution to this?

Airtel often remotely changes the username password for the modem from their end.

ooh, thank you very much, i will call them ASAP

Yup. That has happened to me. I find it a dickish behavior.

When you get the access back, disable remote management in modem settings.

They change the password to your account number